Power Flow Study Of A Compressor Gas Station -...

Power Flow Study Of A Compressor Gas Station

by

Syed Ammar Fida Zaidi

B.A.Sc, Simon Fraser University, 2009

Project Submitted in Partial Fulfillment of the

Requirements for the Degree of

Master of Engineering

in the

School of Engineering Science

Faculty of Applied Sciences

Syed Ammar Fida Zaidi 2015

SIMON FRASER UNIVERSITY

Fall 2015

ii

Approval

Syed Ammar Fida Zaidi

Master of Engineering

Power Flow Study of a Compressor Gas Station

Name:

Degree:

Title:

Supervisory Committee: Chair: Steve Whitmore, Senior Lecturer, MA

Andrew Rawicz Senior Supervisor Professor, Ph.D, P.Eng.

Naeem Tareen External Examiner Senior Electrical Engineer Solaris Management Consultants Inc.

Date Defended/Approved: October 6th, 2015 .

iii

Abstract

A study of the electrical power system in a compressor gas station. The study examines

the load flow throughout the station during the steady state operating condition. A short

circuit study is also conducted to determine the fault availability on the system buses. In

addition, a detailed protective device coordination study and device configuration is

performed to ensure that protective devices are providing overcurrent protection of all

electrical equipment. Finally, an arch flash study is conducted to determine the available

incident energy levels at plant equipment and to provide the specific hazard category for

the equipment.

Keywords: Load Flow; Short Circuit; Time Current Coordination; Protective Device Coordination; Arc Flash; Compressor Gas Station

.

iv

Acknowledgements

I would like to acknowledge Solaris Management Consultants Inc. for allowing me to

utilize this power flow study as my M.Eng. Project. Solaris MCI was also instrumental in

providing the tools and technologies required for conducting this study.

In addition, I appreciate the support and guidance of Pavel Salmine (Electrical and

Controls Specialist) and Naeem Tareen (Senior Electrical Engineer) at Solaris MCI.

Their advice and guidance was crucial in the completion of this study.

v

Table of Contents

Approval .......................................................................................................................... iiAbstract .......................................................................................................................... iiiAcknowledgements ........................................................................................................ ivTable of Contents ............................................................................................................ vList of Tables ................................................................................................................. viiList of Figures ................................................................................................................ viiiList of Acronyms ............................................................................................................. ixIntroductory Image .......................................................................................................... x

INTRODUCTION ............................................................................................................. 1System Representation ................................................................................................... 1Project Assumptions and Clarifications ............................................................................ 2

LOAD FLOW .................................................................................................................. 4Purpose and Scope ......................................................................................................... 4Results ............................................................................................................................ 5

Case Study 1: 138 kV Utility Connection is operating and Attached to the Compressor Station ................................................................................... 5

Case Study 2: Emergency Power Supply by Diesel Generator DG-970 .................. 7

SHORT CIRCUIT STUDY ............................................................................................... 9Purpose and Scope ......................................................................................................... 9Short Circuit Summary Report ......................................................................................... 9Results of Case Study 1 (Utility powered with all CBs Closed) ...................................... 15Results of Case Study 2 (Only Emergency Diesel Generator in Service) ...................... 16Conclusions................................................................................................................... 17

PROTECTIVE DEVICES COORDINATION STUDY ..................................................... 18Purpose and Scope ....................................................................................................... 18Project Assumptions and Clarifications .......................................................................... 19Coordination Analysis .................................................................................................... 20Ground Fault Protection ................................................................................................ 27Conclusion and Results ................................................................................................. 28

ARC FLASH ANALYSIS............................................................................................... 29Purpose and Scope ....................................................................................................... 29System Representation ................................................................................................. 30Computer Software and Calculations ............................................................................ 31Evaluation Study Options .............................................................................................. 32Conclusion and Results ................................................................................................. 32

vi

References ................................................................................................................ 37

APPENDIX A: Load Flow ............................................................................................. 39Load Flow Report (Utility Powered with CB-920A & CB-920B Closed, CB-920TIE

Open) ................................................................................................................... 39Load Flow Report (DG-970 Generator Powered) .......................................................... 44Marginal Report – Voltage Drop before Transformer TAP Adjustment by -

2.5% in Primary .................................................................................................... 49

Appendix B: Short Circuit Analysis Results ............................................................. 51Short Circuit Report (Utility Powered with CB-920A, CB-920B and CB-920TIE

Closed) ................................................................................................................. 51Short Circuit Report (Utility Powered with CB-920A & CB-920B Close, CB-

920TIE Open) ....................................................................................................... 54Short Circuit Report (Utility Powered with CB-920B & CB-920TIE Closed, CB-

920-A Open) ......................................................................................................... 57Short Circuit Report (Utility Powered with CB-920A &CB-920TIE Close, CB-920B

Open) ................................................................................................................... 59Short Circuit Report (DG-970 Generator Powered) ....................................................... 62

APPENDIX C: Time Current Coordination analysis .................................................. 64

vii

List of Tables

Table 1: DC Battery Model Information ........................................................................ 2

Table 2: DG-970 Generator Submittal Data .................................................................. 4

Table 3: Distribution Power Transformer Parameters ................................................ 5

Table 4: MCC Bus Load when Powered by 138 kV Utility (CB-920A & CB-920B Closed, CB-920TIE Open) ............................................................. 5

Table 5: Distribution Transformer Loading ................................................................. 6

Table 6: Voltage Drop on Affected MCC Buses after Transformer Tap Adjustment ............................................................................................. 7

Table 7: MCC Bus Loading when Powered by Emergency Diesel Generator DG-970 .................................................................................................... 8

Table 8: Short-Circuit Summary Report (Utility Powered with all CB-920A, CB-920B, CB-920TIE Closed) .............................................................. 10

Table 9: Short-Circuit Summary Report (Utility Powered with CB-920A & CB-920B Closed, CB-920TIE Open) .................................................... 11

Table 10: Short-Circuit Summary Report (Utility Powered with CB-920A Open, CB-920B & CB-920TIE Closed) ................................................. 12

Table 11: Short-Circuit Summary Report (Utility Powered with CB-920B Open, CB-920A & CB-920TIE Closed) ................................................. 13

Table 12: Short-Circuit Summary Report (DG-970 Generator Powered) ................. 14

Table 13: Per Motor Momentary Duty with VFD Control (motor contribution only) ...................................................................................................... 14

Table 14: MV Motors Momentary Duty with Across-the-line Feed (Bypass mode) .................................................................................................... 14

Table 15: LV MCC Short-Circuit Ratings with Utility Power ..................................... 16

Table 16: LV MCC Short-Circuit Ratings with Emergency DG Power ...................... 17

Table 17: Feeder Circuit Breaker Settings ................................................................. 23

Table 18: NGR System Data and Protective Relay Settings for LV Area ................. 28

Table 19: Arc Flash Hazard Calculations (Utility Powered with CB-920A, CB-920B & CB-920TIE Closed) .................................................................. 34

Table 20: Arc Flash Hazard Calculations (Utility Powered with CB-920A & CB920B Closed, CB-920TIE Open) ...................................................... 34

Table 21: Arc Flash Hazard Calculations (Utility Powered with CB-920B & CB-920TIE Closed, CB-920A Open) .................................................... 35

Table 22: Arc Flash Hazard Calculations (Utility Powered with CB-920A & CB-920TIE Closed, CB-920-B Open) ................................................... 35

Table 23: Arc Flash Hazard Calculations (DG-970 Generator Powered).................. 36

viii

List of Figures

Figure 1: ETAP System Model ...................................................................................... x

Figure 2: Time Current Coordination for TR951C relay (Primary and Secondary) with downstream CBs including LVMCC-934E4 (CB-LVMCC934E-1) .............................................................................. 65


Figure 4: Time Current Coordination of CB-LVMCC934E-1 with Downstream CB-LVMCC934E-2 and CB-LT936 ........................................................ 67

Figure 5: Time Current Coordination of CB-LVMCC944E-1 with downstream CB-LVMCC944E-2 and CB-LT946 ........................................................ 68

Figure 6: Time Current Coordination for TR961F relay (Primary and Secondary) with downstream CBs including LVCC-964E3 (CB-HT983R) ......................................................................................... 69

Figure 7: Time Current Coordination for generator DG-970 with circuit breaker CB-DG970 ............................................................................... 70

Figure 8: Time Current Coordination for generator circuit breaker CB-DG970 with downstream CB-GEN-ATS953 and CB-LVMCC944E-1 ....................................................................................... 71


Figure 10: Time Current Coordination for generator circuit breaker CB-DG970 with downstream CB-GEN-ATS963 and CB-HT983R ............. 73

Figure 11: Time Current Coordination for CB-DG970 with CB-LB979 ..................... 74

Figure 12: TCC for Protection of Motor M-250 with SR469 relay and FUSE-M3 ......................................................................................................... 75

Figure 13: TCC for Protection of Motor M-230 with SR-469 Relay and FUSE-M2 ......................................................................................................... 76


ix

List of Acronyms

LV Low Voltage

MV Medium Voltage

VFD Variable Frequency Drive = ASD (Automatic Speed Drive)

MCC Motor Control Center

UPS Uninterruptible Power Supply

CB Circuit Breaker

TR Transformer

DG Diesel Generator

MVSW Medium Voltage Switchgear

BH Building Heater

LT Lighting Transformer

.

x

Introductory Image

Figure 1: ETAP System Model

1

INTRODUCTION

This report summarizes the electrical power system studies for the Compressor Gas Station. This report includes the following:

• Load flow analysis to determine the steady state operating characteristics, verifyactive and reactive power flow in the electrical system, and provide loading andvoltage profiles in the system for different loading conditions.

• Short circuit study with three-phase and single-line to ground short circuitcalculations providing the prospective fault availability at the 600 V and 6.9 kVbusses.

• Protective device coordination ensures that protective devices provide overcurrentprotection of downstream electrical equipment and their TCC curves coordinate withother protective equipment along the current path.

• Arc flash study provides the available incident energy levels at plant equipment,details the specific hazard category for the equipment and the associated personalprotective equipment (PPE) required while working with the equipment.

System Representation

Compressor Station 15-27 was modeled using ETAP software Version 12.6.0C. The ETAP model was developed using the construction revision SMCI single line diagrams as well as technical data provided by vendors and information available at the time of preparation of this report.

A 138kV BC Hydro distribution power line provides power to two 25/34/42MVA 138kV-6900V power transformers. The transformers feed into a 7.2kV switchgear.

The 7.2kV switchgear distributes power to two MV MCCs and two step-down 6900V-600V power transformers. The MV ASDs are used to start the sales compressor motors (via MVMCC-934A and MVMCC-944B) and are capable of synchronizing and transferring them to the 60Hz utility power bus via contactors.

The LV side of the power transformers (6900V-600V) is connected to LV MCCs feeding the 600V MCCs downstream. The 600V MCCs contain the necessary circuit breakers, contactors, ASDs and motor starters for the facility loads. The 600V system consists of:

LVMCC-964F: Building Q-960

LVMCC-964E3: Building Q-960

LVMCC-954C1: Building Q-950



LV-MCC-934E4: Building Q-930

Power is distributed from the MCCs to individual motors and to 600V-120/208V transformers located strategically in the facility. Each of these transformers is

2

connected to a 120/208V three-phase distribution panel. There are two 125VAC UPS sized to provide power to the plant critical power loads (including security system and CCTVs/cameras, all control panels including MV VFD control power and network communications) for four hours.

Power cables are XLPE RW90 600V TECK90 with copper conductors. Instrumentation and control devices utilize either XLPE RW90 600V TECK90 or XLPE RW90 300V ACIC. The building devices are wired to the junction boxes and multi-core home run cables connect to the AC distribution panel and PLC control panel.

The station electrical ground grid consists of driven piles under the pipe rack and all buildings bonded via #2/0 AWG conductors to structural steel, motors, junction boxes, control panels and cable tray.

There is a 1500 kW, 600 V emergency diesel generator (DG-970) connected to the emergency LV MCC (LVMCC-974E1). Automatic open transition transfer switches ATS-953 and ATS-963 distribute power to emergency loads in LVMCC-944E5, LVMCC-934E4, LVMCC-954E2 and LVMCC-964E3. The generator is sized to provide standby power to facility lighting & heating, electric heat tracing, instrument air compressors, and UPS systems. The generator capacity will not include any remaining non-essential loads.

Project Assumptions and Clarifications

Plant AC UPS DC Battery

The model of the DC battery used in this project is not available in the ETAP software used for this study. As a result, the closest available model in ETAP was utilized to fulfill the requirement of this study. The table below shows the battery purchased for installation and the available model in ETAP.

Table 1: DC Battery Model Information

Manufacturer Model AH Voltage SC Current

Internal Resistance

Purchased for Installation

EXIDE Absolyte GNB 6-90G13

520 120 3891 0.000514

Used in ETAP Model

EXIDE DD/ V 85 510 120 3987 0.003100

DC Circuit Breaker:

The model and specifications of the circuit breaker used in the DC UPS system to protect the battery is specified as SACE Tmax at 300 A. The closest available model for DC circuit breaker in the ETAP software model is ABB SACE T5H Tmax at 300 A.

Study Cases

For the optimum system functionality, it was necessary to consider two operational cases in the Load Flow study:

• Normal case with 138 kV utility supplying power to the compressor station

• Emergency case with only DG-970 generator power supply available

3

For Short circuit and Arc Flash studies, the normal case is further divided into four studies:

• Normal case with All circuit breakers Closed

• Normal case with CB-920-TIE circuit breaker Open

• Normal case with CB-920-A circuit breaker Open

• Normal case with CB-920-B circuit breaker Open

Lumped Loads

The ETAP software version 12.6.0C has a license limit of 1000 buses for one project. In order to reduce the bus consumption in the project, most static loads below 40 KW and motors below 50 HP were lumped together into a single load. These lumped loads had generic tag names that did not match the original tags used in the project. To avoid any confusion in the final result, the tags of these lumped loads are omitted from the final results tables and data. However, these lumped loads are included in all calculations used to achieve the final results.

Variable Frequency Device (VFD) Configuration

VFD protective system parameters are not provided by the manufacturer but it is known that the overcurrent protection is instantaneous without any delay. In case of a short circuit or arc flash on MCC buses, no noticeable effect is expected in the circuit between VFD and Motor. Therefore, the final results of this study do not include the effect of those motors that are connected to the system through a VFD. All other motors that are directly connected to the power system across the line are included in the final results.

Study Criteria

The criteria used for the study include the following:

• All electrical equipment must operate within its rated capacity.

• The steady state operating voltage at the load busses in the power system must be within ±5% of equipment rated voltage.

• Available symmetrical and asymmetrical fault levels should not exceed the bus bracing and protective equipment interrupting capacity.

• Protective settings should provide overcurrent protection for downstream devices and coordination with upstream and downstream protective devices.

• Protective device settings should provide reduction of the available arc flash energy to the level where reasonable PPE may be applied.

4

LOAD FLOW

Purpose and Scope

The purpose of this load flow analysis is to investigate the performance of the Compressor Station power system under operating and emergency conditions and to make recommendations where required on any operational adjustment and equipment change to ensure satisfactory overall system operation.

Load flow calculations were performed to define loading of generators, transformers, and cables, as well as the voltage level at each bus and the voltage drop on each feeder circuit for a steady-state condition. The voltage drop calculations are incorporated directly into the calculations of the steady-state load flows.

Toshiba MV VFDs rated for 6.6 kV with acceptable voltage variation +/- 10%. Therefore, MVSW-921 Bus A and B under any operational conditions shall not exceed 6750V by means of the LTC on the 25 MVA transformers. This also implies a permanent adjustment to the tap changers on transformers TR-951C and TR-951D to sustain 600 V on the downstream MCCs.

This study demonstrates:

• The available options to regulate capacity of generators under different operational conditions.

• That voltage profiles are satisfactory at all voltages available in the power system.

• That available transformer tap changes are sufficient for required voltage regulation.

• That MCC equipment rated capacity is sufficient and is not overloaded under normal operation.

• That distribution transformers, lighting panels and associated cables rated capacities determined based on available load are not overloaded.

• The diesel emergency generator DG-970 has sufficient capacity to power essential services.

Table 2: DG-970 Generator Submittal Data

GEN-ID

Rated (V)

Rated (kW)

Reactances (PU) Time Constants (Sec.)

Subtrans. Direct Axis

X’d (PU)

Transient Saturated

X’d (PU)

Synchron. Direct Axis

X’d (PU)

Short Circuit Subtrans. Direct Axis T'd (sec)

Short Circuit Transient Direct Axis T’d (sec)

Armature Ta

(sec)

DG-970

600 1500 0.19 0.28 1.55 0.035 0.65 0.2

5

Table 3: Distribution Power Transformer Parameters

TXMR-ID

HV/LV Rated (V)

Rated (kVA)

Impedance (%) X/R

Ratio Cooling

Off Circuit Taps

BIL

%IZ %IR %IX HV

(kV)

LV

(kV)

TR-951C

6900∆/

600Y-347 V

2000 5.69 0.80 5.634 7.10 ONAN/ONAF HV

±2.5%±5.0% FCBN

95 30

TR-961F

6900∆/

600Y-347 V

2000 5.69 0.80 5.634 7.10 ONAN/ONAF HV

±2.5%±5.0% FCBN

95 30

Results

The load flow results for two case studies are summarized below. Detailed results that provide the loading and voltage drop profile of the equipment and cables for both case studies are provided in Appendix A.

Case Study 1: 138 kV Utility Connection is operating and Attached to the Compressor Station

This case study considers the 138 kV utility running and connected to the network. Loading factors in the model were adjusted to ensure that the power demand values were accurate. After applying the appropriate loading factors, detailed load flow analysis was conducted.

This scenario illustrates that the power system is properly designed to run in normal operation. The total bus loading is shown in Table 4 below.

Table 4: MCC Bus Load when Powered by 138 kV Utility (CB-920A & CB-920B Closed, CB-920TIE Open)

BUS-ID Rated (V)** Rated

(A)

Load

(V)

Load

(kVA) Load (A)

Power

Factor

(%)

PFCC-923A 6900 1200 6747 6793 572.7 -

MVMCC-934A 6900 3000 6747 11867 1000.5 93

TR951C-6.9kV-PR*

6900 3000 6747 1743 147 92

TR961F-6.9kV-PR*

6900 3000 6748 1359 114.8 98

6

BUS-ID Rated (V)** Rated

(A)

Load

(V)

Load

(kVA) Load (A)

Power

Factor

(%)

TR951C-600V-SEC*

600 2500 593 1699 1690.6 94

TR961F-600V-SEC *

600 2500 596 1340 1319.8 98

MVMCC-944B 6900 3000 6748 5932 500.1 93

LVMCC-954C1 600 2500 592 1699 1690.6 94

LVMCC-954E2 600 1600 591 820 818.2 94

LVMCC-934E4 600 800 589 70 69.8 95

LVMCC-944E5 600 800 589 70 69.7 95

LVMCC-964F 600 2500 595 1340 1319.8 98

LVMCC-964E3 600 800 592 508 502.1 99

* = Transformer primary and secondary bus loading

** - 6750 V is 1 pu voltage

Table 5: Distribution Transformer Loading

TXMR-ID HV/LV Rated (V) Rated (kVA)

Load (kVA)

PF

(On Primary)

Recommended Tap Setting

Utilization Factor (%)

TR-951C 6900∆/

600Y-347 V 2000 1745 0.922 Pr. -5% 87.25

TR-961F 6900∆/

600Y-347 V 2000 1379 0.981 Pr. -5% 68.95

Considering the requirement for 6750V on MVSW-921 bus A and B, the -5% tap adjustment on the HV side of TR-951C and TR-961F compensates for voltage drop at LVMCC-954C1, LVMCC-954E2, LVMCC-934E4, LVMCC-944E5, LVMCC-964F and LVMCC-964E3.

Calculated plant-wide steady state voltage drops in the points of utilization do not exceed 5% as specified by the CEC. The worst-case available voltage drop is 4.6% at the input terminals of lighting panel LT-946G in LVMCC-944E5.

To improve the situation with voltage drop, it is recommended to adjust TR-951C and TR-961F taps to increase voltage level at the downstream equipment terminals. Based on vendor information, the distribution transformers TR-951C & TR-961F offer a ±2.5% and ±5% tap adjustment on the HV side.

The below list of distribution transformers have mandatory (-5%) tap adjustment.

7

• Required tap settings (-5% FCBN): TR-951C and TR-961F

Voltage drop values were calculated for all major buses in the compressor station and after applying the tap adjustments on the distribution transformers the resulting voltage drop percentage is shown in Table 6 below. The initial voltage drop values for all buses before the transformer tap adjustments are shown in 0.

Table 6: Voltage Drop on Affected MCC Buses after Transformer Tap Adjustment

Bus-ID Rated (V) Operating (V) % Vd

LVMCC-954C1 600 592 1.4

LVMCC-954E2 600 591 1.5

LVMCC-934E4 600 589 1.8

LVMCC-944E5 600 589 1.8

LVMCC-964F 600 595 0.1

LVMCC-964E3 600 592 1.4

Case Study 2: Emergency Power Supply by Diesel Generator DG-970

In case of emergency power interruption from the utility power supply, all loads connected to LVMCC-954E2 and LVMCC-964E3 will be powered from the DG-970 generator. Load shedding during emergency operation was not considered so the normal operating load was used in the calculations.

Maximum projected generator load flow data is as follows:

• DG-970: 1389 kW, 1450 kVA (Winter load)

The results of the load flow study show that when only DG-970 diesel generator supplies power to the LVMCC-954E2 and LVMCC-964E3, the required power flow is below the 1500 kW/1875 kVA nominal rating of the generator.

Calculated load flow power factor is 95.8% on the diesel generator DG-970.

The bus loading data for case study 2 is presented in Table 7.

.

8

Table 7: MCC Bus Loading when Powered by Emergency Diesel Generator DG-970

BUS-ID Rated (V) Rated

(A)

Load

(V)

Load

(kVA) Load (A)

Power

Factor

(%)

LVMCC-974E1 600 2500 599.7 1450 1395.7 95.8

LVMCC-954E2 600 1600 596.3 863 834.6 93.8

LVMCC-934E4 600 800 594.2 73 70.9 95.0

LVMCC-944E5 600 800 593.7 73 70.9 95.0

LVMCC-964E3 600 800 581.2 505 500.6 99.3

A detailed load flow analysis for each bus going down to individual loads is shown in Appendix A for both cases.

Conclusion

After conducting a detailed load flow analysis of the 15-27 Compressor Station 600 V distribution system, the demand on the existing system and effects of possible load addition were determined. The conclusions for the two case studies are described below.

The available generation capacity for both cases is sufficient to prevent variations in voltage and frequency in the steady-state operation and during available step loading.

The rated current capacity of transformers, cables and other power distribution equipment is sufficient for the application and will not be overloaded during normal operation.

According to available results and depending on the actual voltage delivered by the utility it will be required to step up the transformer taps (TR-951C and TR-961F) by 5% to meet the 5% overall voltage drop limits and bring the voltage drop at the 600V switchgear and MCC buses to 2% or lower. Initiated in the system voltage drop on the LV MCC buses and individual feeders by the cables and equipment impedance within the required limits and does not present an issue for the equipment operation.

9

SHORT CIRCUIT STUDY

Purpose and Scope

ETAP software Version 12.6.0C has been utilized for short circuit analysis.

The purpose of this study is to determine the prospective fault availability for the 6.9 kV and 600 V systems. This study will be used to analyze:

• The available symmetrical and asymmetrical fault duties on all the 6.9 kV and 600 V busses

• The equipment is capable of safely withstanding and interrupting the presently available fault current

For the purpose of this study, the scope of the short circuit calculations, documentation and equipment evaluation were limited to portions of the distribution electrical system defined by the SMCI design scope.

To implement the short circuit study the quasi-steady state fault analysis techniques were used that represent the Compressor Station power system at steady state condition. Phasors are used to represent system voltages, currents, and impedances at fundamental frequency. The power system modeling and the resulting computation techniques are based on the assumption that the system and its components can be represented by linear models. Utilizing linearity simplifies considerably the necessary calculations.

Based on the same measures, intermediate system data was omitted from this report for clarity. The omitted data include fault current phase shift data for each bus node and Thevenin equivalent impedance values in complex number notation (R+jX). These data are used for calculation purposes in the program and are not of interest for most readers.

Short Circuit Summary Report

This section includes a summary of the short circuit results for 3-phase faults, line to ground faults (LG), line-to-line faults (LL) and line to line to ground (LLG) faults for all LVMCC buses. It also includes the short circuit faults for buses feeding into three 7000 HP compressor motors M210, M230, M250 as well as MVMCC-934A, MVMCC-944B, MVSW-921A and MVSW-921B.

Available 138 kV utility parameters for fault contribution as follow:

- 3-Phase contribution 1336.54 MVAsc with X/R =5.292

- 1-Phase contribution 346.23 MVAsc with X/R=6.855

Two main delta-wye transformers TR-912A and TR-912B locate in substation and step down the transmission line 138 kV to the compressor station 6.9 kV MV distribution. The main parameters of the transformers as follow: 25 MVA ONAN/ONAF/ONAF 138 kV/6.9 kV %Z=8.33

10

Table 8: Short-Circuit Summary Report (Utility Powered with all CB-920A, CB-920B, CB-920TIE Closed)

1/2 Cycle - 3-Phase, LG, LL, and LLG Fault Currents Prefault Voltage = 100 % of the Bus Nominal Voltage Bus 3-Phase Fault (kA) Line-to-Ground

Fault (kA)

Line-to-Line Fault

(kA)

*Line-to-Line-to-

Ground (kA)

ID kV Real Imag. Mag. Real Imag. Mag. Real Imag. Mag. Real Imag. Mag.

BUS M210 6.75 4.627 -

38.683

38.958 0.100 0.000 0.100 33.500 4.007 33.739 -

33.525

-

4.007

33.764

BUS M230 6.75 4.634 -

38.808

39.084 0.100 0.000 0.100 33.609 4.013 33.848 -

33.634

-

4.013

33.872

BUS M250 6.75 4.627 -

38.683

38.958 0.100 0.000 0.100 33.500 4.007 33.739 -

33.525

-

4.007

33.764

BUS

MVMCC-

934A

6.75 4.627 -

38.683

38.958 0.100 0.000 0.100 33.500 4.007 33.739 -

33.525

-

4.007

33.764

BUS

MVMCC-

944B

6.75 4.634 -

38.808

39.084 0.100 0.000 0.100 33.609 4.013 33.848 -

33.634

-

4.013

33.872

BUS

MVSW-921-

A

6.75 4.603 -

39.243

39.512 0.100 0.000 0.100 33.985 3.987 34.218 -

34.010

-

3.987

34.243

BUS

MVSW-921-

B

6.75 4.603 -

39.243

39.512 0.100 0.000 0.100 33.985 3.987 34.218 -

34.010

-

3.987

34.243

Bus-

TR951C-

600V

0.60 4.958 -

32.258

32.636 0.002 0.000 0.002 27.936 4.294 28.264 -

27.936

-

4.294

28.265

Bus-

TR961F-

600V

0.60 5.534 -

31.057

31.547 0.002 0.000 0.002 26.896 4.793 27.320 -

26.897

-

4.793

27.321

Load-

ATS953

0.60 5.484 -

30.722

31.208 0.002 0.000 0.002 26.606 4.749 27.026 -

26.606

-

4.749

27.027

Load-ATS-

963

0.60 7.568 -

24.617

25.754 0.002 0.000 0.002 21.319 6.554 22.304 -

21.320

-

6.554

22.304

LVMCC-

934E4

0.60 11.055 -9.313 14.455 0.002 0.000 0.002 8.065 9.574 12.518 -8.066 -

9.574

12.518

LVMCC-

944E5

0.60 10.040 -7.410 12.478 0.002 0.000 0.002 6.417 8.695 10.806 -6.418 -

8.695

10.807

LVMCC-

954C1

0.60 5.067 -

31.296

31.704 0.002 0.000 0.002 27.103 4.388 27.456 -

27.104

-

4.388

27.457

LVMCC-

954E2

0.60 5.723 -

29.425

29.976 0.002 0.000 0.002 25.483 4.956 25.960 -

25.483

-

4.956

25.961

LVMCC-

964E3

0.60 8.275 -

22.382

23.863 0.002 0.000 0.002 19.383 7.167 20.666 -

19.384

-

7.167

20.666

LVMCC-

964F

0.60 5.581 -

30.223

30.734 0.002 0.000 0.002 26.174 4.834 26.616 -

26.174

-

4.834

26.617

N-TR951C-

6.9kV

6.75 8.013 -

34.518

35.436 0.100 0.000 0.100 29.893 6.939 30.688 -

29.918

-

6.939

30.713

N-TR961F-

6.9kV

6.75 11.366 -

22.450

25.164 0.100 -

0.001

0.099 19.443 9.844 21.792 -

19.467

-

9.843

21.815

11

Table 9: Short-Circuit Summary Report (Utility Powered with CB-920A & CB-920B Closed, CB-920TIE Open)

1/2 Cycle - 3-Phase, LG, LL, and LLG Fault Currents

Prefault Voltage = 100 % of the Bus Nominal Voltage

Bus 3-Phase Fault (kA) Line-to-Ground Fault

(kA)

Line-to-Line Fault

(kA)

*Line-to-Line-to-

Ground (kA)


BUS

M210

6.75 2.213 -

25.261

25.358 0.050 0.000 0.050 21.877 1.917 21.961 -

21.889

-

1.916

21.973

BUS

M230

6.75 2.025 -

21.998

22.091 0.050 0.000 0.050 19.051 1.753 19.132 -

19.063

-

1.753

19.144

BUS

M250

6.75 2.213 -

25.261

25.358 0.050 0.000 0.050 21.877 1.917 21.961 -

21.889

-

1.916

21.973

BUS

MVMCC-

934A

6.75 2.213 -

25.261

25.358 0.050 0.000 0.050 21.877 1.917 21.961 -

21.889

-

1.916

21.973

BUS

MVMCC-

944B

6.75 2.025 -

21.998

22.091 0.050 0.000 0.050 19.051 1.753 19.132 -

19.063

-

1.753

19.144

BUS

MVSW-

921-A

6.75 2.198 -

25.426

25.521 0.050 0.000 0.050 22.020 1.904 22.102 -

22.032

-

1.904

22.114

BUS

MVSW-

921-B

6.75 2.011 -

22.113

22.204 0.050 0.000 0.050 19.150 1.742 19.229 -

19.163

-

1.742

19.242

Bus-

TR951C-

600V

0.60 4.651 -

31.104

31.449 0.002 0.000 0.002 26.937 4.028 27.236 -

26.937

-

4.028

27.236

Bus-

TR961F-

600V

0.60 5.084 -

29.542

29.976 0.002 0.000 0.002 25.584 4.403 25.960 -

25.584

-

4.403

25.960

Load-

ATS953

0.60 5.153 -

29.684

30.128 0.002 0.000 0.002 25.707 4.462 26.092 -

25.708

-

4.462

26.092

Load-

ATS-963

0.60 7.032 -

23.701

24.722 0.002 0.000 0.002 20.526 6.090 21.410 -

20.526

-

6.090

21.410

LVMCC-

934E4

0.60 10.819 -9.344 14.296 0.002 0.000 0.002 8.092 9.370 12.380 -8.092 -

9.370

12.381

LVMCC-

944E5

0.60 9.869 -7.456 12.369 0.002 0.000 0.002 6.457 8.547 10.712 -6.457 -

8.547

10.712

LVMCC-

954C1

0.60 4.760 -

30.214

30.587 0.002 0.000 0.002 26.166 4.122 26.489 -

26.167

-

4.122

26.489

LVMCC-

954E2

0.60 5.388 -

28.479

28.984 0.002 0.000 0.002 24.663 4.666 25.101 -

24.664

-

4.666

25.101

LVMCC-

964E3

0.60 7.729 -

21.649

22.987 0.002 0.000 0.002 18.748 6.694 19.907 -

18.749

-

6.694

19.908

LVMCC-

964F

0.60 5.136 -

28.791

29.245 0.002 0.000 0.002 24.934 4.448 25.327 -

24.934

-

4.448

25.328

N-

TR951C-

6.9kV

6.75 3.866 -

23.532

23.847 0.050 0.000 0.050 20.379 3.348 20.652 -

20.392

-

3.348

20.665

N-

TR961F-

6.9kV

6.75 5.595 -

16.213

17.151 0.050 0.000 0.050 14.041 4.846 14.853 -

14.053

-

4.846

14.865

12

Table 10: Short-Circuit Summary Report (Utility Powered with CB-920A Open, CB-920B & CB-920TIE Closed)

1/2 Cycle - 3-Phase, LG, LL, and LLG Fault Currents Prefault Voltage = 100 % of the Bus Nominal Voltage Bus 3-Phase Fault (kA) Line-to-Ground

Fault (kA)

Line-to-Line Fault (kA) *Line-to-Line-to-

Ground (kA)


BUS M210 6.75 2.434 -

28.592

28.695 0.050 0.000 0.050 24.761 2.108 24.851 -

24.774

-

2.108

24.86

3

BUS M230 6.75 2.437 -

28.618

28.722 0.050 0.000 0.050 24.784 2.111 24.874 -

24.797

-

2.111

24.88

6

BUS M250 6.75 2.434 -

28.592

28.695 0.050 0.000 0.050 24.761 2.108 24.851 -

24.774

-

2.108

24.86

3

BUS

MVMCC-

934A

6.75 2.434 -

28.592

28.695 0.050 0.000 0.050 24.761 2.108 24.851 -

24.774

-

2.108

24.86

3

BUS

MVMCC-

944B

6.75 2.437 -

28.618

28.722 0.050 0.000 0.050 24.784 2.111 24.874 -

24.797

-

2.111

24.88

6

BUS

MVSW-921-

A

6.75 2.407 -

28.832

28.933 0.050 0.000 0.050 24.970 2.085 25.056 -

24.982

-

2.085

25.06

9

BUS

MVSW-921-

B

6.75 2.407 -

28.832

28.933 0.050 0.000 0.050 24.970 2.085 25.056 -

24.982

-

2.085

25.06

9

Bus-

TR951C-

600V

0.60 4.720 -

31.485

31.836 0.002 0.000 0.002 27.266 4.087 27.571 -

27.267

-

4.087

27.57

2

Bus-

TR961F-

600V

0.60 5.268 -

30.340

30.794 0.002 0.000 0.002 26.275 4.562 26.668 -

26.275

-

4.562

26.66

8

Load-

ATS953

0.60 5.232 -

30.029

30.481 0.002 0.000 0.002 26.006 4.531 26.397 -

26.006

-

4.531

26.39

8

Load-ATS-

963

0.60 7.280 -

24.195

25.266 0.002 0.000 0.002 20.953 6.304 21.881 -

20.954

-

6.304

21.88

2

LVMCC-

934E4

0.60 10.89

8

-

9.340

14.353 0.002 0.000 0.002 8.089 9.438 12.430 -

8.089

-

9.438

12.43

0

LVMCC-

944E5

0.60 9.927 -

7.445

12.408 0.002 0.000 0.002 6.448 8.597 10.746 -

6.448

-

8.597

10.74

6

LVMCC-

954C1

0.60 4.831 -

30.572

30.951 0.002 0.000 0.002 26.476 4.183 26.805 -

26.477

-

4.183

26.80

5

LVMCC-

954E2

0.60 5.471 -

28.794

29.309 0.002 0.000 0.002 24.936 4.738 25.383 -

24.937

-

4.738

25.38

3

LVMCC-

964E3

0.60 7.989 -

22.049

23.451 0.002 0.000 0.002 19.095 6.919 20.309 -

19.095

-

6.919

20.31

0

LVMCC-

964F

0.60 5.320 -

29.546

30.021 0.002 0.000 0.002 25.587 4.607 25.999 -

25.588

-

4.607

25.99

9

N-TR951C-

6.9kV

6.75 4.523 -

26.408

26.793 0.050 0.000 0.050 22.870 3.917 23.203 -

22.882

-

3.917

23.21

5

N-TR961F-

6.9kV

6.75 7.695 -

19.284

20.762 0.050 0.000 0.050 16.700 6.664 17.981 -

16.713

-

6.664

17.99

2

13

Table 11: Short-Circuit Summary Report (Utility Powered with CB-920B Open, CB-920A & CB-920TIE Closed)




(kA)

Line-to-Line Fault (kA) *Line-to-Line-to-

Ground (kA)


BUS

M210

6.75 2.435 -28.570 28.673 0.050 0.000 0.050 24.742 2.109 24.832 -24.754 -

2.109

24.84

4

BUS

M230

6.75 2.439 -28.596 28.700 0.050 0.000 0.050 24.765 2.112 24.855 -24.777 -

2.112

24.86

7

BUS

M250

6.75 2.435 -28.570 28.673 0.050 0.000 0.050 24.742 2.109 24.832 -24.754 -

2.109

24.84

4

BUS

MVMC

C-

934A

6.75 2.435 -28.570 28.673 0.050 0.000 0.050 24.742 2.109 24.832 -24.754 -

2.109

24.84

4

BUS

MVMC

C-944B

6.75 2.439 -28.596 28.700 0.050 0.000 0.050 24.765 2.112 24.855 -24.777 -

2.112

24.86

7

BUS

MVSW

-921-A

6.75 2.409 -28.810 28.910 0.050 0.000 0.050 24.950 2.086 25.037 -24.962 -

2.086

25.04

9

BUS

MVSW

-921-B

6.75 2.409 -28.810 28.910 0.050 0.000 0.050 24.950 2.086 25.037 -24.962 -

2.086

25.04

9

Bus-

TR951

C-

600V

0.60 4.719 -31.482 31.834 0.002 0.000 0.002 27.264 4.087 27.569 -27.265 -

4.087

27.57

0

Bus-

TR961

F-600V

0.60 5.268 -30.337 30.791 0.002 0.000 0.002 26.273 4.562 26.666 -26.273 -

4.562

26.66

7

Load-

ATS95

3

0.60 5.232 -30.027 30.479 0.002 0.000 0.002 26.004 4.531 26.396 -26.004 -

4.531

26.39

6

Load-

ATS-

963

0.60 7.279 -24.193 25.265 0.002 0.000 0.002 20.952 6.304 21.880 -20.953 -

6.304

21.88

0

LVMC

C-

934E4

0.60 10.89

7

-9.340 14.352 0.002 0.000 0.002 8.089 9.437 12.429 -8.089 -

9.437

12.43

0

LVMC

C-

944E5

0.60 9.926 -7.445 12.408 0.002 0.000 0.002 6.448 8.596 10.746 -6.448 -

8.596

10.74

6

LVMC

C-

954C1

0.60 4.830 -30.570 30.949 0.002 0.000 0.002 26.474 4.183 26.803 -26.475 -

4.183

26.80

3

LVMC

C-

954E2

0.60 5.471 -28.792 29.307 0.002 0.000 0.002 24.935 4.738 25.381 -24.935 -

4.738

25.38

1

LVMC

C-

964E3

0.60 7.988 -22.048 23.450 0.002 0.000 0.002 19.094 6.918 20.308 -19.094 -

6.918

20.30

9

LVMC

C-964F

0.60 5.320 -29.544 30.019 0.002 0.000 0.002 25.586 4.607 25.997 -25.586 -

4.607

25.99

8

N-

TR951

C-

6.9kV

6.75 4.522 -26.389 26.773 0.050 0.000 0.050 22.853 3.916 23.186 -22.866 -

3.916

23.19

9

N-

TR961

F-

6.9kV

6.75 7.689 -19.274 20.751 0.050 0.000 0.050 16.691 6.659 17.971 -16.704 -

6.659

17.98

2

14

Table 12: Short-Circuit Summary Report (DG-970 Generator Powered)




(kA)

Line-to-Line Fault

(kA)

*Line-to-Line-to-

Ground (kA)


LVMCC-

934E4

0.60 3.853 -7.258 8.217 0.002 0.000 0.002 6.253 3.508 7.170 -

6.253

-

3.508

7.170

LVMCC-

944E5

0.60 4.056 -6.541 7.696 0.002 0.000 0.002 5.616 3.658 6.702 -

5.617

-

3.658

6.703

LVMCC-

954E2

0.60 1.195 -10.276 10.345 0.002 0.000 0.002 9.051 1.273 9.140 -

9.051

-

1.273

9.140

LVMCC-

964E3

0.60 2.176 -5.893 6.282 0.002 0.000 0.002 5.114 1.987 5.487 -

5.115

-

1.987

5.487

LVMCC-

974E1

0.60 0.865 -10.751 10.786 0.002 0.000 0.002 9.498 0.997 9.550 -

9.498

-

0.997

9.550

MV motors fault contribution is considered as one of the fault current sources on the 6.9 kV distribution system.

The MV VFD do not contribute short-circuit current and therefore are not considered in our design

The results of the short circuit calculations under the VFD control presented as follows:

Table 13: Per Motor Momentary Duty with VFD Control (motor contribution only)

Momentary Duty Summary

Symm. kA RMS X/R Ratio Asymm. kA RMS

Motor M-210 3.793 0.3 3.793

Motor M-250 3.793 0.3 3.793

Motor M-230 3.599 0.3 3.599

The results of the short circuit calculations when motor transferred to across-the-line feed presented as follows:

Table 14: MV Motors Momentary Duty with Across-the-line Feed (Bypass mode)

Momentary Duty Summary for the Single Motor in Bypass

Symm. kA RMS X/R Ratio Asymm. kA RMS

Motor M-210 36.165 9.5 51.596

Motor M-250 35.522 9.2 50.328

Motor M-230 35.784 9.2 50.704

The available results were utilized in sizing calculations for MV motor feeder cables.

The more detailed results are presented in the Short Circuit Summary Report pages.

15

Results of Case Study 1 (Utility powered with all CBs Closed)

This case shows the fault level with the plant in normal operating configuration and all intended for this stage compressor motors M-210, M-230 and M-250 are running and connected across the line. This situation characterized the maximum fault level contribution to the compressor station electrical system at maximum supply voltage.

All other prospective fault level contributors are Q-740 Desand Building transfer pump motors (P-741A and P-741B) rated at 125 HP and controlled by the across-the-line motor starter in the LVMCC-964F. LVMCC-974E1 in Diesel Generator Building includes Radiator Fan motor RF-972 rated at 75 HP. Air Compressor motors K-811A and K-811B, both rated at 60 HP, can contribute to fault on LVMCC-954E2 and LVMCC-954C1 respectively.

Other motor loads are not considered as fault contributors in this study due to their small size or VFD control of the motor.

The power distribution transformers and their corresponding impedances significantly impact the available fault energy on the MCC buses.

From the results available, the highest fault currents are present on MVMCC-944B for 6.9 kV and on TR-951C-600V and TR-961F-600V buses for 600V. In this instance, the values available on the MVMCC-944B bus will be considered as a reference number for the MV power system analysis. In this instance, the values available on the TR-951C-600V bus (33kA) will be considered as a reference number for the LV power system analysis.

From the above tables we can see that the maximum ANSI Symmetrical 3-phase fault current at the compressor station LVMCC-954C1 is 33 kA, which is well below its 65kA bus bracing rating. MVMCC-934A and MVMCC-944B buses have 50kA bus bracing ratings. The maximum available symmetrical fault currents for MVMCC-934A and MVMCC-944B are in the range of 39 kA and 39 kA in the current configuration, which is below available bus bracing ratings.

The highest X/R ratio calculated for the LVMCC-954C1 bus is 6.4, which is higher than UL 845 standard level suggested to manufacturers for the equipment basis design and performance. With presence of the substantial DC component in the fault current, it is advisable to compare the LVMCC-954C1 bus bracing rating and protective devices interrupting ratings with asymmetrical 3-phase fault current value as well. Calculated LVMCC-954C1 bus RMS asymmetrical fault is 41.9 kA, which is still below the bus bracing rating.

Estimated peak current value for fault duties on LVMCC-954C1 is 72.2 kA and does not exceed the tested MCC (141.9 kA) peak current capacity. The same conclusion is applied to the protective devices peak ratings utilized in design. The smallest protective device peak rating is 186 kA, which belongs to Square D model HL circuit breaker that is above the maximum peak current calculated for LV MCC protective devices.

The rest of LVMCCs results of the peak current duties estimation for utility power supply are presented in Table 15 below.

16

Table 15: LV MCC Short-Circuit Ratings with Utility Power

MCC

ID

Manufacturer

Model

MCC Amps/Bus

Bracing

(A/kA)

Max Sym. RMS Fault

(kA)

X/R

Ratio

Fault

PF

(%)

Equipment

Rated Peak Current

(kA)

Available

Peak Current

(kA)

LVMCC-954C1

Square D Model 6

2500/65 31.70 6.4 14.2 141.9 72.20

LVMCC-954E2

Square D Model 6

1600/65 29.98 5.2 18.9 141.9 65.69

LVMCC-964F

Square D Model 6

2500/65 30.73 5.5 18.3 141.9 68.00

LVMCC-964E3

Square D Model 6

1200/65 23.86 2.7 33.8 141.9 44.38

LVMCC-934E4

Square D Model 6

800/65 14.46 0.8 73.8 141.9 20.95

LVMCC-944E5

Square D Model 6

800/65 12.48 0.7 81.2 141.9 17.91

Results of Case Study 2 (Only Emergency Diesel Generator in Service)

This case shows the fault level within the emergency compressor station-operating configuration, with one DG-970 diesel generator in service at its maximum fault level contribution at available supply voltage.

The calculations show that the RMS Symmetrical 3-phase fault current is 10.78 kA and RMS Asymmetrical 3-phase fault current is 16.59 kA at the emergency LVMCC-974E1, which is well below the 65kA bus bracing rating.

The X/R ratio calculated for the LVMCC-974E1 with emergency power supply is 16.5 kA which is higher than UL 845 standard level (X/R=4.899) suggested to manufacturers for the equipment basis design. With presence of a substantial DC component in the fault current, it is advisable to consider LVMCC-974E1 maximum available instantaneous peak current.

Estimated peak current value for fault duties on LVMCC-974E1 is 27.18 kA and do not exceed the emergency motor control centre (141.9 kA) and adjacent circuit breaker (186 kA) peak current capacity.

The rest of LVMCCs results of the peak current duties estimation for emergency generator power supply presented in the following table.

17

Table 16: LV MCC Short-Circuit Ratings with Emergency DG Power

MCC

ID

Manufacturer

Model

MCC Amps/Bus

Bracing

(A/kA)

Max Sym. RMS Fault

(kA)

X/R

Ratio

Fault

PF

(%)

Equipment

Rated Peak Current

(kA)

Available

Peak Current

(kA)

LVMCC-954E2

Square D Model 6

1600/65 10.345 9.8 10.3 141.9 25.26

LVMCC-964E3

Square D Model 6

1200/65 6.282 2.8 32.4 141.9 11.77

LVMCC-934E4

Square D Model 6

800/65 8.154 1.9 46.3 141.9 13.89

LVMCC-944E5

Square D Model 6

800/65 7.696 1.6 53.9 141.9 12.49

LVMCC-974E1

Square D Model 6

2500/65 10.786 16.5 6.2 141.9 27.87

Conclusions

Conclusion Case Study 1

The results show that all electrical equipment operates within its ratings.

The symmetrical fault levels at the 600 V MCCs ranges from 6.282 kA to 31,70 kA, safely below the (65kA) bus bracing rating and the adjoining (85 kA/100 kA/200 kA) protective devices interrupting ratings.

The available peak current values at the 600 V MCCs ranges from 17.91 kA to 72.20 kA, safely below the MCC bus bracing peak withstand rating 141.9 kA and the smallest value of protective equipment peak withstand rating at 141.9 kA.

The system contribution and all 6.6 kV motors fault contribution data and time constants were used to extrapolate conductor short circuit withstand parameters. The proper conductor sizes were defined based on this information.

The short circuit calculation results confirm that all electrical equipment operates within the requisite short circuit ratings during normal and fault conditions.

Conclusion Case Study 2

The results show that all electrical equipment operates within its ratings with emergency power supply.

The symmetrical/asymmetrical fault levels at the 600V MCCs range from 14.1 kA to 22.2 kA, safely below the (65kA) bus bracing rating and the adjoining (85 kA/100 kA/200 kA) protective devices interrupting ratings.

The available peak current value at the 600 V LVMCC-954E2 with emergency DG-970 generator power supply is only 37.5 kA, safely below the MCC bus bracing peak withstand rating 141.9 kA and protective equipment peak withstand rating 186.0 kA.

The short circuit calculation results confirm that all electrical equipment operates within the requisite short circuit ratings during normal operating conditions.

18

PROTECTIVE DEVICES COORDINATION STUDY

Purpose and Scope

There are three fundamental objectives of overcurrent coordination presented in this study.

• The main objective is life safety requirements. Selected devices are rated to carry and interrupt maximum available load currents as well as withstand and interrupt maximum available fault currents. Life safety requirements shall never be compromised.

• The second objective is equipment protection. Protection requirements are met if overcurrent devices are set above load operating levels and below equipment damage curves.

• The last objective is selectivity or protective device coordination. The coordination study is a time-current study of the protective devices in series from the source to the utilization equipment. Overcurrent coordination is the application of current activated devices in the plant electrical system, which, in response to fault or overload, will clear the fault while removing the minimum amount of equipment from service.

This study is a comparison of the individual overcurrent device time-current curves to determine where the curves overlap causing a large portion of the electrical system to be de-energized in order to clear the fault. The time-current curves show graphically how quickly the overcurrent devices respond to current of a specific magnitude.

Prior to performing an arc flash study, the overcurrent protection device settings must be determined. These settings affect the time duration that an arcing fault will exist during an arc flash occurrence. Therefore, the settings reduce the amount of incident energy released during an arcing fault.

Coordination studies take into consideration the transformer magnetizing inrush current, full-load current, hot-load and cold-load pick-up, and coordination time intervals for cascaded devices.

As a side benefit of a coordination study, the interrupting ratings of all protective devices, short circuit withstand ratings of conductors and switches are all checked for adequacy. Inadequate equipment ratings can result in extensive damage to the equipment during faults and system operation and may introduce hazards to plant operating personnel.

The ETAP software version 12.6.0C was used in conducting this study. The program produces time versus current coordination drawings with one-line diagrams and setting reports.

19

Project Assumptions and Clarifications

For the optimum system functionality, it was necessary to consider two operational cases in the coordination study:

• Normal case with 138 kV utility supplying power to the plant

• Emergency case with only DG-970 generator operating

Derived protective device settings should be applicable for all operationalconditions and not require field adjustments.

Additionally, the following information was considered for the coordination study:

• System voltage levels as presented in section 1

• Generator and transformer ratings and impedance data as per available frommanufacturer

• Existing MV phase protection including relay models, numbers and settings, CT-ratios and TCC curves as specified in Orbis Engineering power study report

• Data for the system under study:

o Transformer ratings, impedance data and protection points as specified insection 1

o Protective devices ratings including momentary and interrupting duties as pervendor documentation

o Ground fault system protection with CT ratios, excitation curves and windingresistances

o Time-current curves for the protective devices as specified by manufacturers

o Cable sizes and length as presented in cable schedules

o Thermal (I²t) curves for cables and rotating machines per manufacturerspecifications

o ASD and UPS system ratings and input impedance values as specified bymanufacturers

• Short circuit and load current data:

o Maximum and minimum momentary (first cycle) short-circuit currents at MCCbusses and EDC terminals as it calculated in Short Circuit Study

o Maximum and minimum interrupting duties (first 5 cycles and above) short-circuit currents at major buses

o Estimated maximum and minimum arcing and bolted ground faults at majorbusses in Arc Flash Analysis

o Maximum load currents as calculated in the Load Flow Study

o The voltage base was 600 V for the calculations and all current values wereconverted to this voltage base

20

Each curve includes a simplified single line diagram, which graphically describes the system studied. The location and shape of each device curve is controlled by the settings on the device. These settings include long-time pickup, long-time delay, short-time pickup, short-time delay, and instantaneous.

Maximum load ampacity and short-circuit currents are indicated during protective device characteristic curve adjustments. These numbers define the adjustment area for the protective device settings.

Certain time intervals were maintained between the characteristic curves of the protective devices. These intervals ensure correct sequential operation of the devices due to certain operational speed of circuit breakers and damage characteristics of fuses.

In some instances, selective coordination of cascaded protective devices, may be sacrificed to achieve the fastest possible protective device operation for an arc flash energy control determined by EnCana Arc Flash requirements.

Coordination Analysis

This study provides settings for the main feeder circuit breakers and individual branch circuit breakers with the available adjustable elements.

Proper arrangement of the circuit breaker characteristic curves with respect of the protected equipment performance characteristics presents the first step of the protection settings. Operational and damage curves for equipment, such as generators, motors, and cables are also plotted to assess the level of protection provided for the equipment and to provide a graphical representation of the protection achieved. For example, the main application for the CB-LVMCC934E-2 circuit breaker is overcurrent protection of the LVMCC-934E4 bus. Additionally, the settings of CB-LVMCC934E-2 account for arc flash energy control on the same bus.

The coordination of the series circuit breaker selective curves from power source to the load branches was performed. All load feeder circuit breakers and J-type fuses in the MCCs have fixed trip unit characteristic curves (see Appendix C). The coordination procedure for these protective devices leads to a simple configuration that the series protective device TCC curves do not overlap with each other.

Only representative load circuit breakers were drafted in composite time-current graph form and selectively coordinated with upstream protective devices (Appendix C). Since a majority of the equipment has the same protective settings, one particular curve is valid for multiple sets of equipment.

Appendix C shows the Time Current Coordination (TCC) graphs for the results of the calculations in the normal power system operation and Emergency power generation.

The electrical system of the EnCana Compressor Station contains two 6.9 kV motor control centers (MCMCC-934A and MVMCC-944B) with multiple downstream branches connected to the bus. Three of MV switchgear branches contain a fused contactor assembly with a GE Multilin 469 protection relay. It is considered that all across-the-line motor starters a fused disconnect with Shawmut (Ferraz) A072B fuses, Toshiba MV vacuum contactors HCV-5HA, GE Multilin SR469 motor protection relays, MV rated cables, and a ABB 7000HP motors sized for the reciprocating compressor application.

21

Typical protection philosophy between protective and switching devices in MV fused contactor motor starter employs the protection relay for only overload protection and uses the fuse for short-circuit protection of the equipment. This approach makes the possible risk of contact welding for a fault with fault current in excess of the contactor interrupting rating practically negligible. The border of the relay protection area is determined by the value of the contactor short circuit breaking current. Therefore, the fuse will take care of all fault current values beyond the contactor breaking capacity. Following this logic, the relay overload settings were utilized and has to leave the short circuit settings de-activated after the relay commissioning.

M-210 feeder protection settings

SR469-K210-O

PHASE TOC

Pickup

1.15 x CT primary amps

Curve Type

Standard Overload Curve

Time Delay Multiplier 5

GROUND TOC

Trip Pickup


Time Delay 0 ms

22


SR469-K220-OL

PHASE TOC

Pickup


Curve Type



GROUND TOC

Trip Pickup


Time Delay 0 ms


SR469-K230-OL

PHASE TOC

Pickup


Curve Type



GROUND TOC

Trip Pickup


Time Delay 0 ms

All results of the ground fault protective relay settings and coordination with other ground fault protective devices presented in Appendix C.

23

Table 17 below shows the feeder circuit breaker settings for circuit breakers that were used in the calculations.

Table 17: Feeder Circuit Breaker Settings

Breakers

Name/Type Description Model Frame/Sensor/Plug Settings

CB-ATS963-1

(LVMCC-964F)

Square-D MICROLOGIC 5.0

PKA 1200.0A/

800.0A

LT Pickup =1 (800A)

LT Band = 0.5

ST Pickup = 3 (2400A)

ST Band = 0.1 (I2T = OUT)

Inst. Pickup = 12 (9600A)

CB-ATS953-1

(LVMCC-954C1)


PKA 1200.0A/

1200.0A

LT Pickup =1 (1200A)

LT Band = 0.5




CB-ATS953

(LVMCC-974E1)


PKA 1200.0A/

1200.0A


LT Band = 0.5




CB-LB979 Square-D MICROLOGIC 5.0

PKA 1200.0A/

1000.0A


LT Band = 2

ST Pickup = 1.5 (1500A)



CB-ATS963

(LVMCC-974E1)


PKA 1200.0A/

800.0A

LT Pickup =1 (800A)

LT Band = 0.5

ST Pickup = 1.5 (1200A)



CB-DG970 ABB E3N-A 2000.0A/

2000.0A

LT Pickup =0.9 (1800A)

LT Band = 3




CB-AHF955C1 Square-D MICROLOGIC 3.3 (PP)

LL 400.0A/

400.0A

Ir = 350 A

Tr = 16.0

Ii = 12 x In (4800A)

CB-AHF965F1 Square-D MICROLOGIC 3.3 (PP)

LL 400.0A/

400.0A

Ir = 350 A

Tr = 16.0

Ii = 12 x In (4800A)

24

Breakers


CB-AHF965F2 Square-D MICROLOGIC 3.3 (PP)

LL 400.0A/

400.0A

Ir = 350 A

Tr = 16.0

Ii = 12 x In (4800A)

CB-E4 Square-D MICROLOGIC 3.2 (PP)

HL 250.0A/

250.0A

Ir = 150 A

Tr = 16.0

Ii = 15 x In (2250A)

CB-E5 Square-D MICROLOGIC 3.2 (PP)

HL 250.0A/

250.0A

Ir = 150 A

Tr = 16.0

Ii = 15 x In (2250A)

CB-E5M Square-D MICROLOGIC 3.3 (PP)

LL 400.0A/

400.0A

Ir = 150 A

Tr = 4.0

Ii = 4 x In (1600A)

CB-E4M Square-D MICROLOGIC 3.3 (PP)

LL 400.0A/

400.0A

Ir = 150 A

Tr = 4.0

Ii = 4 x In (1600A)

CB-LT916A Square-D MICROLOGIC 3.2

HL 150.0A/

150.0A

Ir = 110 A

Tr = 0.5

Ii = 8 x In (1200A)

CB-LT926C Square-D MICROLOGIC 3.2

HL 150.0A/

150.0A

Ir = 150 A

Tr = 0.5

Ii = 10 x In (1500A)

CB-LT956H Square-D PowerPact HL 150.0A/

100.0A

Rating Plug = 100 A

Inst. = 13 (1300A)

CB-LT976E Square-D MICROLOGIC 3.2

HL 150.0A/

150.0A

Ir = 110 A

Tr = 0.5

Ii = 8 x In (1200A)

CB-HT983Q Square-D MICROLOGIC 3.2

HL 150.0A/

150.0A

Ir = 110 A

Tr = 0.5

Ii = 8 x In (1200A)

CB-LT986K Square-D PowerPact HL 150.0A/

100.0A

Rating Plug = 100 A

Inst. = 13 (1300A)

CB-HT963P Square-D MICROLOGIC 3.2

HL 150.0A/

150.0A

Ir = 110 A

Tr = 0.5

Ii = 8 x In (1200A)

CB-HT983R Square-D MICROLOGIC 3.2

HL 150.0A/

150.0A

Ir = 110 A

Tr = 0.5

Ii = 8 x In (1200A)

CB-LT986M Square-D PowerPact HL 150.0A/

100.0A

Rating Plug = 100 A

Inst. = 13 (1300A)

CB-K612A Square-D Powerpact JL 250.0A/

250.0A

Thermal Curve

Inst = 1250 A

25

Breakers


CB-K612B Square-D Powerpact JL 250.0A/

250.0A

Thermal Curve

Inst = 1250 A

CB-P741A Square-D Powerpact JL 250.0A/

250.0A

Thermal Curve

Inst = 10

CB-P741B Square-D Powerpact JL 250.0A/

250.0A

Thermal Curve

Inst = 10

CB-LVMCC934E4

(LVMCC-954E2)

Square-D MICROLOGIC 3.2 (PP)

HL 150.0A/

150.0A

Ir = 150 A

Tr = 16.0

Ii = 15 x In (2250A)

CB-LVMCC944E5

(LVMCC-954E2)

Square-D MICROLOGIC 3.2 (PP)

HL 150.0A/

150.0A

Ir = 150 A

Tr = 16.0

Ii = 15 x In (2250A)

CB-K615 Square-D MICROLOGIC 5.0

PKA 1200 A/

800 A

LT PU = Fixed (800 A)

LT Band = Fixed

Inst = 6 (4800A)

CB-C226 Square-D Powerpact HL 150.0A/

30.0A

Rating Plug = 14 A

Inst. = 8 (112A)

CB-CF220 Square-D Powerpact HL 150.0A/

50.0A

Rating Plug = 29 A

Inst. = 8 (232A)


30.0A

Rating Plug = 14 A

Inst. = 8 (112A)


50.0A

Rating Plug = 29 A

Inst. = 8 (232A)


30.0A

Rating Plug = 14 A

Inst. = 8 (112A)

CB-CF260 Square-D Powerpact HL 150.0A/

50.0A

Rating Plug = 29 A

Inst. = 8 (232A)

CB-P352A Square-D Powerpact HL 150.0A/

30.0A

Rating Plug = 14 A

Inst. = 8 (112A)

CB-P352B Square-D Powerpact HL 150.0A/

30.0A

Rating Plug = 14 A

Inst. = 8 (112A)


30.0A

Rating Plug = 14 A

Inst. = 8 (112A)


30.0A

Rating Plug = 14 A

Inst. = 8 (112A)


30.0A

Rating Plug = 14 A

Inst. = 8 (112A)

CB-P628 Square-D Powerpact HL 150.0A/

30.0A

Rating Plug = 14 A

Inst. = 8 (112A)


30.0A

Rating Plug = 14 A

Inst. = 8 (112A)

26

Breakers



50.0A

Rating Plug = 29 A

Inst. = 8 (232A)


30.0A

Rating Plug = 14 A

Inst. = 8 (112A)


30.0A

Rating Plug = 14 A

Inst. = 8 (112A)

CB-P775C Square-D Powerpact HL 150.0A/

30.0A

Rating Plug = 14 A

Inst. = 8 (112A)

CB-VF978C Square-D Powerpact HL 150.0A/

30.0A

Rating Plug = 14 A

Inst. = 8 (112A)

CB-RF972 Square-D Powerpact HL 150.0A/

150.0A

Rating Plug = 97 A

Inst. = 8 (776A)

CB-VF218A Square-D Powerpact HL 150.0A/

30.0A

Rating Plug = 14 A

Inst. = 8 (112A)

CB-VF218B Square-D Powerpact HL 150.0A/

30.0A

Rating Plug = 14 A

Inst. = 8 (112A)


30.0A

Rating Plug = 14 A

Inst. = 8 (112A)

CB-VF218D Square-D Powerpact HL 150.0A/

30.0A

Rating Plug = 14 A

Inst. = 8 (112A)


30.0A

Rating Plug = 14 A

Inst. = 8 (112A)


30.0A

Rating Plug = 14 A

Inst. = 8 (112A)


30.0A

Rating Plug = 14 A

Inst. = 8 (112A)


30.0A

Rating Plug = 14 A

Inst. = 8 (112A)


30.0A

Rating Plug = 14 A

Inst. = 8 (112A)


30.0A

Rating Plug = 14 A

Inst. = 8 (112A)


30.0A

Rating Plug = 14 A

Inst. = 8 (112A)


30.0A

Rating Plug = 14 A

Inst. = 8 (112A)


30.0A

Rating Plug = 14 A

Inst. = 8 (112A)

CB-SAF938A Square-D Powerpact HL 150.0A/

30.0A

Rating Plug = 14 A

Inst. = 8 (112A)

27

Breakers


CB-SAF938B Square-D Powerpact HL 150.0A/

30.0A

Rating Plug = 14 A

Inst. = 8 (112A)

CB-SAF948A Square-D Powerpact HL 150.0A/

30.0A

Rating Plug = 14 A

Inst. = 8 (112A)

CB-SAF948B Square-D Powerpact HL 150.0A/

30.0A

Rating Plug = 14 A

Inst. = 8 (112A)

Ground Fault Protection

The 600 V systems are high resistance grounded via a neutral grounding resistor (NGR) connected on the LV side of the distribution transformers (TR-951C and TR-961F) and to the neutral point of the emergency generator DG-970. The main advantage of this method is elimination of ground-fault flash hazards with substantial point-of-fault damage.

In the event of a ground fault, an alarm signal from the ground fault relay will signal to compressor station main PLC to alert operations as an automatic shutdown does not occur. The decision of when to shutdown and address the ground fault is left to operations. There are three status signals from ground fault protective relay provided to the main PLC: Ground Fault, Resistor Fault and Unit Healthy. There is no need for ground-fault protection coordination between the MV and LV power distribution systems.

The NGRs are designed to dissipate the required amount of energy and not exceed the temperature limitations of IEEE Standard 32-1972. They have a continuous rating, which is capable of withstanding rated current for an indefinite period of time. The continuous temperature rise for the resistive element is 385°C. Startco SE-330 NGR monitor protective relay with ER-600VC sensing resistor and EFCT-26 current transformer were selected. The SE-330 continuously measures NGR resistance in an unfaulted system, and it will produce alarm signal if resistance varies from the calibrated value.

The NGR selection was based on system charging current and expected duration of running with a ground fault. If the ground fault escalates to a phase-to-phase fault, the phase overcurrent protection will isolate the circuit.

All results of the ground fault protective relay settings and coordination with other ground fault protective devices presented in Appendix C.

28

Table 18: NGR System Data and Protective Relay Settings for LV Area

NGR Location

System Voltage

(V)

Neutral-Grounding Resistor

Current Transformer

Sensing

Resistor

Expect.

Charging Current

(A)

SE-330 Settings

(Ohms)

Let-Through

Current

(A)

Model

CT Ratio

Trip

Level (%/A)

Trip

Time

(S)

Vn Trip Level

(V)

Pulse Period

(S)

TR-951C-N

600/347

173.5 2 EFCT-26

5/0.05

ER-600VC

0.48 20/1 2 130 N/A

TR-961F-N

600/347

173.5 2 EFCT-26

5/0.05

ER-600VC

0.37 20/1 2 130 N/A

DG-970-N

600/347

173.5 2 EFCT-26

5/0.05

ER-600VC

0.43 20/1 2 130 N/A

Conclusion and Results

Proper calculations were performed to review the selection of fuses, protective relay characteristics and settings, ratios and characteristics of associated current transformers, and low-voltage circuit breaker trip characteristics and settings. This study confirms that all circuit breakers, protective relays, automatic transfer switches, and fuses are sized adequately for the load and fault currents available in the Phase 1 Compressor Station power system.

The settings and selectivity of the circuit breakers and fuses will provide protection within industry standards as shown by the time-current curves in Appendix C. The time-current curves are positioned to provide the maximum selectivity to minimize system disturbance during fault clearing.

29

ARC FLASH ANALYSIS

Purpose and Scope

The purpose of this study is to determine the potential arc flash hazard on the electrical equipment at the compressor station electrical system and how these hazards can be mitigated.

Arc Flash analysis estimates the amount of the incident energy released in the event of an arc fault and determines the required flash protection boundaries. As a safety survey the Arc Flash analysis identifies the potentially dangerous area of the compressor station, properly label them, ensure adequate work procedures are in place and specify Personal Protective Equipment (PPE) for work on or near energized electrical equipment.

NFPA 70E defines an arc flash hazard as “a dangerous condition associated with the release of energy caused by an electric arc.” Arc flashing can be extremely dangerous, capable of damaging or destroying equipment and posing a safety threat to plant personnel. By analyzing a system’s potential Arc Flash Hazard, we can determine the different hazard categories that are relevant with specific equipment. See Table 5.0, Appendix B for EnCana PPE breakdown according to NFPA 70E.

Arc Flash Boundary is defined as a distance from the arc source where the onset of second-degree burns can occur. This is typically defined by medical research as 1.2 cal/cm².

Incident Energy is defined as the amount of energy impressed on the surface, a specific distance away from the source during an electrical arc event. It can also be called surface energy density. Incident energy is measured in cal/cm².

Utilized in the study Trip/Delay Time is a protective device characteristic that can be found in manufacturer data. For circuit breakers with integral trip units, the manufacturer time-current curves include both tripping time and clearing time.

Proper Warning Labels must be prepared for installation on all plant electrical equipment and especially on equipment that may remain energized during maintenance or service.

The 2012 editions of CSA Z462 and NFPA 70E include new tables for DC equipment hazard/risk category classification. Part of the table covers voltages over 100 volts and below 250 volts. The other part of the table covers voltages from 250 volts to 600 volts. Although the tables do not cover voltages below 100 volts, it does not indicate there is no arc flash danger below this voltage. In fact, there are potential arc flash hazards even below 50 volts, depending on various factors, including the amount of short circuit current that is available.

The NFPA 70E tables for DC indicate that for voltages above 100 and arcing current higher than or equal to 1000 amps, the arc flash boundary is at least 36 inches. Anyone within this boundary must wear arc-rated clothing, arc-rated face shield with wrap around protection to protect the entire head (or flash hood), hardhat, safety goggles, hearing protection and leather work shoes (see table 1). To protect against electric shock, the tables require rubber-insulating gloves with leather protectors.

30

As well, Table 4B of CSA Z462-12 requires that insulating gloves be used when working on a battery. Essentially, all of this equipment must be used for all battery maintenance with voltages above 100 volts to comply with the standard.

The most common stationary battery configurations UPS are 24 volt (telecommunications, cellular), 48 volt (telecommunications), 125 volt (switchgear, UPS). The majority of the 125 volt installations are ungrounded systems. The risk of an arc flash to ground in ungrounded systems is non-existent as long as there is not a ground fault condition.

Most 24 and 48-volt systems are grounded, but the voltage is so low that the risk of arc flash is reduced, but not eliminated.

For battery installations on open racks on ungrounded systems (typical for 125 volt and UPS batteries), the potential for arc flash concerns rest mainly with the main battery terminals. If there are cabinets associated with the battery, such as disconnects and distribution, then there is probably a high arc flash potential in these locations. Extreme precautions are warranted for battery disconnects and DC distribution cabinets when they are energized.

System Representation

ETAP Version 12.6.0C Arc Flash Evaluation module was used in conducting this study. The program calculates the incident energy and arc flash boundary for every location in the power system. Incident energy and arc flash boundaries are calculated following IEEE 1584 standard. PPE requirements are specified from a user-defined clothing library. Additionally, clearing times were reduced based on current-limiting capabilities.

The following is other information that was used in this study to represent the power distribution system:

• The generators fault contribution was modeled for both three-phase to ground fault and single-phase to ground fault. Also minimum and maximum contributions were modeled based on how the diesel generator source was contributing to the 600V system.

• The arc flash hazard analysis was performed according to the IEEE 1584-2002/2004a, NFPA 70E 2009 Annex D.7 and CSA-Z462 Annex D7. The arc flash hazard analysis was performed in conjunction with the short-circuit analysis and the protective device time-current coordination analysis.

• Circuits 240V or less fed by single transformer rated less than 125 kVA are omitted from the calculations and assumed to have a hazard risk category 0 per NFPA 70E.

• Working distances are based on IEEE 1584 standard. The calculated arc flash protection boundaries were determined using those working distances as a preset values in ETAP software.

• When performing incident energy calculations on the line side of a main breaker, the line side and load side contributions were included in the fault calculations.

• Arc flash calculations are based on actual overcurrent protective devices clearing time. A maximum clearing time of 2 seconds will be used based on IEEE 1584-2002 section B 1.2. Where is not physically possible to move outside of the flash

31

protection boundary in less than 2 seconds during an arc flash event, a maximum clearing time based on the specific location was utilized.

• 125 VDC switchgear battery set X was neglected in the DC arc flash analysis. This bank has an extremely limited total capacity and the contributions are deemed negligible.

• Fault contributions from battery chargers were neglected due to negligible contributions. The core saturable reactors on the AC input side limit the available fault contributions to a minute value.

• The results on the arc flash diagrams are displayed in Incident Energy Level, (Cal/Cm^2), Typical Working Distance to Arc Flash Source (In).

• Considering the difficulties to determine how to classify the tasks to be performed for different type of equipment that are operating at different voltage levels, EnCana Corporation developed their own Protective Measures Matrix (PMM). This “lookup” table lists different tasks to be performed on energized equipment and their associated risk levels. Allowed PPE categories were reduced to 0, 1, 2 and are described in detail in Appendix D.

Computer Software and Calculations

ETAP Version 12.6.0C Arc Flash was used in conducting this study. The method specified in IEEE 1584-2002/2004a Edition, NFPA 70E 2009 Annex D.7 and CSA-Z462 Annex D.7 standards is used to calculate the arcing fault current, incident energy and arc flash boundary.

This method uses the following calculation to determine the incident energy (E) at each bus:

E = 4.184*Cf*En*(t/0.2)(610^X/D^X), where

E = incident energy (J/cm^2)

1En = Incident energy (J/cm^2) normalized for a arcing duration of 0.2s and working distance of 610mm

Cf = is 1.0 for voltage above 1 kV and 1.5 for voltage below 1 kV

t = arcing duration in seconds

D = working distance from arc (mm)

X = is the distance exponent

Once the arc flash incident energy is calculated, a hazard category is chosen based on this value. The hazard value is then used to determine the personal protective equipment needed when working on exposed electrical equipment.

1 En is determined from the arcing and bolted fault currents at the bus.

32

Evaluation Study Options

The equations used to calculate the magnitude of an arcing fault are relative to the available 3-phase bolted fault current. Single-line to ground and line-to-line faults are not directly considered when calculating arcing fault or incident energy. It was recognized that many arcing faults are initiated by a line-to-ground fault. The arc flash equations in the IEEE 1584 standard are relative to the available three-phase bolted fault current.

It is generally accepted that arcing faults that begin as line-to-line or line-to-ground faults quickly escalate into three-phase faults as the air ionizes across the phases.

The following specific assumptions are applied to the arc flash study for 15-27 Saturn Sister Compressor Station PH 1:

• Conductor and buses impedances and X/R ratios were modeled closely in order to obtain realistic short circuit values

• The trip time is determined for all protective devices located in the branch that contains the first trip device and the device with the fastest trip time

• Worker is stationary during the entire arc flash incident (constant working distance).

• Induction motors contribute continuous sub-transient current for 1 cycle, unless they are excluded from arc flash calculations if they are less than 50 HP

• In the branches with applied current-limiting fuses, the current-limiting range is assumed to start where fuse clearing curve drops below 0.01 sec

• Upstream branch devices are properly coordinated with downstream branch devices in protective devices coordination study. The mis-coordination ratio defined as 80%. By utilizing the selection option “Check upstream protective devices for mis-coordination”, the next upstream protective device will be included in the search. The device that clears the arcing fault first is used

• Ground fault and motor overload devices are not included into consideration

• If the trip time obtained from the time current curve is larger than the maximum protection trip time defined as 2 sec., the maximum protection trip time is used

• For equipment operated below 1 kV, arc flash boundaries are calculated based on incident energy equation

Conclusion and Results

Using the methods and criteria described in the previous section, the arc flash analysis was conducted for all relevant equipment. The arc flash hazard calculation results are summarized below for four cases. These results display the Incident Energy Level (Cal/cm2) and Typical Working Distance to Arc Flash Source (mm) on all the analyzed busses.

From the adjacent utility protective devices to the LV individual feeder protection, all protective devices coordinated settings were adjusted to achieve the fastest reaction during the arc flash events. The settings were calculated for all possible power supply scenarios.

33

All electrical equipment installed in the LVMCC-974E1, LVMCC-954E2, LVMCC-934E4 and LVMCC-944E5 protected by the corresponding feeder molded case circuit breakers with fixed protective characteristic curves. MVMCC-934A, MVMCC-944B, LVMCC- 964E3, LVMCC-954C1, LVMCC-954C2 and LVMCC-964F main buses are protected by upstream protective devices. Multilin T60 and F60 protective relays and Littlefuse PGR-8800 arc-flash protection relays are used in conjunction with Square D upper MCC feeder circuit breaker.

Initiated arcing fault current on the input terminals of MCC buses, circuit breakers, disconnect switches, 600V and 120/208V distribution panels, etc. is lower than three-phase bolted fault current. The TR-951C and TR-961F transformer secondary protective relays and downstream circuit breaker settings on the TCC curve demonstrates 0.001 sec. minimal delay of an instantaneous component tripping for the available arc flash current. These settings allow achieving as low as 8 cal/cm² of arc flash energy on LVMCC-954C1 and LVMCC-964F buses. According to Encana classification, the level of incident energy above 8 cal/cm² requires use of level 2 PPE.

All available flash protection boundaries and incident energy values were calculated at all significant locations in the electrical distribution system and will be presented on SLD MVMCC-934A, MVMCC-944B, LVMCC-954C1, LVMCC-964F, LVMCC-974E1, LVMCC-954E2, LVMCC-964E3, LVMCC-934E4 and LVMCC-944E5 drawings.

Combined results of arc flash studies for all possible combinations of the power sources are presented in five tables below to show the arc flash results for different scenarios.

The short-circuit calculations and the corresponding incident energy calculations were performed for multiple system scenarios. This allowed retrieving maximum and minimum contributions of fault current magnitude and comparing them with the protective devices settings. After the comparison, the greatest incident energy was uniquely reported for each equipment location.

Special consideration is applied to the situation when the tie breaker is closed during 20 second and both feeders circuit breakers are closed as well. This corresponds to the maximum available fault level on all buses.

It is important to consider that the area in the power transformer TR-951C and TR-961F secondary bushings are exposed to the substantially higher energy levels (8.8 – 9 cal/cm²) during possible faults and arc flash events.

34

Table 19: Arc Flash Hazard Calculations (Utility Powered with CB-920A, CB-920B & CB-920TIE Closed)

Table 20: Arc Flash Hazard Calculations (Utility Powered with CB-920A & CB920B Closed, CB-920TIE Open)

35

Table 21: Arc Flash Hazard Calculations (Utility Powered with CB-920B & CB-920TIE Closed, CB-920A Open)

Table 22: Arc Flash Hazard Calculations (Utility Powered with CB-920A & CB-920TIE Closed, CB-920-B Open)

36

Table 23: Arc Flash Hazard Calculations (DG-970 Generator Powered)

37

References

Institute of Electrical and Electronics Engineers, Inc. (IEEE), 1986, IEEE 141: Recommended Practice for Electric Power Distribution and Coordination of Industrial and Commercial Power Systems, Piscataway, New Jersey: Systems Design Subcommittee of the IEEE Power Systems Engineering Committee

Institute of Electrical and Electronics Engineers, Inc. (IEEE), 1986, IEEE 242: Recommended Practice for Protection and Coordination of Industrial and Commercial Power Systems, Piscataway, New Jersey: Systems Design Subcommittee of the IEEE Power Systems Engineering Committee

Institute of Electrical and Electronics Engineers, Inc. (IEEE), 1986, IEEE 551: Calculating Short-Circuit Currents in Industrial and Commercial Power Systems, Piscataway, New Jersey: Systems Design Subcommittee of the IEEE Power Systems Engineering Committee

Institute of Electrical and Electronics Engineers, Inc. (IEEE), 1986, IEEE 399: Recommended Practice for Industrial and Commercial Power System Analysis, Piscataway, New Jersey: Systems Design Subcommittee of the IEEE Power Systems Engineering Committee

Institute of Electrical and Electronics Engineers, Inc. (IEEE), 1986, IEEE 241: Recommended Practice for Electric Power Systems in Commercial Buildings, Piscataway, New Jersey: Systems Design Subcommittee of the IEEE Power Systems Engineering Committee

Institute of Electrical and Electronics Engineers, Inc. (IEEE), 1986, IEEE 1015: Recommended Practice for Applying Low-Voltage Circuit Breakers Used in Industrial and Commercial Power Systems, Piscataway, New Jersey: Systems Design Subcommittee of the IEEE Power Systems Engineering Committee

Institute of Electrical and Electronics Engineers, Inc. (IEEE), 1986, IEEE 1584: Guide for Performing Arc-Flash Hazard Calculations, Piscataway, New Jersey: Systems Design Subcommittee of the IEEE Power Systems Engineering Committee

38

Institute of Electrical and Electronics Engineers, Inc. (IEEE), 1986, IEEE 519: IEEE Recommended Practices and Requirements for Harmonic Control in Electrical Power Systems, Piscataway, New Jersey: Systems Design Subcommittee of the IEEE Power Systems Engineering Committee

Canadian Standards Association (CSA), 2009, CSA C22.1-09: Canadian Electrical Code (CEC), Part 1, Toronto, ON: CEC, Part I Technical Committee

Canadian Standards Association (CSA), 2009, CSA Z462-08: Workplace Electrical Safety, Toronto, ON: CEC, Part I Technical Committee

Canadian Standards Association (CSA), 2009, CSA C22.2 No. 254-05: Motor Control Centres, Toronto, ON: CEC, Part I Technical Committee

American National Standards Institute (ANSI), 2002, ANSI C57.12.00: Standard General Requirements for Liquid-Immersed Distribution, Power, and Regulating Transformers, Rosslyn, Virginia, National Electrical Manufacturers Association

American National Standards Institute (ANSI), 2002, ANSI C37.013: Standard for Low Voltage AC Power Circuit Breakers Used in Enclosures, Rosslyn, Virginia, National Electrical Manufacturers Association

American National Standards Institute (ANSI), 2002, ANSI C37.010: Standard Application Guide for AC High Voltage Circuit, Rosslyn, Virginia, National Electrical Manufacturers Association

The National Fire Protection Association (NFPA), 2014, NFPA 70: National Electrical Code, Quincy, Massachusetts, The National Fire Protection Association

The National Fire Protection Association (NFPA), 2014, NFPA 70E: Standard for Electrical Safety in the Workplace, Quincy, Massachusetts, The National Fire Protection Association

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APPENDIX A: Load Flow

Load Flow Report (Utility Powered with CB-920A & CB-920B Closed, CB-920TIE Open)

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Load Flow Report (DG-970 Generator Powered)

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Bus Loading Summary Report

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Marginal Report – Voltage Drop before Transformer TAP Adjustment by -2.5% in Primary

Device ID Type Condition Rating/Limit Unit Operating %

Operating Phase Type

Bus_BH709 Bus Under Voltage 0.600 kV 0.551 91.9 3-Phase

Bus_BH719 Bus Under Voltage 0.600 kV 0.551 91.9 3-Phase

Bus_BH7X9B Bus Under Voltage 0.600 kV 0.557 92.9 3-Phase

Bus_CF214A-1 Bus Under Voltage 0.600 kV 0.562 93.6 3-Phase


Bus_CF214B-1 Bus Under Voltage 0.600 kV 0.562 93.6 3-Phase


Bus_CF214C-1 Bus Under Voltage 0.600 kV 0.562 93.6 3-Phase














Bus_HT963P Bus Under Voltage 0.600 kV 0.556 92.7 3-Phase

Bus_HT983Q Bus Under Voltage 0.600 kV 0.556 92.6 3-Phase

Bus_HT983R Bus Under Voltage 0.600 kV 0.556 92.7 3-Phase

Bus_HVAC958B Bus Under Voltage 0.600 kV 0.557 92.8 3-Phase

Bus_HVAC958D Bus Under Voltage 0.600 kV 0.557 92.8 3-Phase

Bus_HVAC968B Bus Under Voltage 0.600 kV 0.565 94.1 3-Phase

Bus_HVAC968D Bus Under Voltage 0.600 kV 0.565 94.1 3-Phase

Bus_K811A Bus Under Voltage 0.600 kV 0.556 92.7 3-Phase

Bus_K811B Bus Under Voltage 0.600 kV 0.558 93.1 3-Phase

Bus_LT016Y Bus Under Voltage 0.600 kV 0.554 92.3 3-Phase

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Device ID Type Condition Rating/Limit Unit Operating % Operating

Phase Type

Bus_LT916A Bus Under Voltage 0.600 kV 0.557 92.8 3-Phase

Bus_LT926C Bus Under Voltage 0.600 kV 0.558 92.9 3-Phase

Bus_LT936F Bus Under Voltage 0.600 kV 0.556 92.7 3-Phase

Bus_LT946G Bus Under Voltage 0.600 kV 0.555 92.4 3-Phase

Bus_LT956H Bus Under Voltage 0.600 kV 0.560 93.3 3-Phase

Bus_LT966J Bus Under Voltage 0.600 kV 0.558 93.0 3-Phase

Bus_LT976E Bus Under Voltage 0.600 kV 0.558 92.9 3-Phase

Bus_LT986K Bus Under Voltage 0.600 kV 0.556 92.7 3-Phase

Bus_LT986M Bus Under Voltage 0.600 kV 0.558 93.0 3-Phase

Bus_P324B-1 Bus Under Voltage 0.600 kV 0.562 93.6 3-Phase

Bus_P324B-2 Bus Under Voltage 0.600 kV 0.553 92.1 3-Phase

Bus_P652 Bus Under Voltage 0.600 kV 0.553 92.2 3-Phase

Bus_P741A Bus Under Voltage 0.600 kV 0.560 93.3 3-Phase

Bus_UPS957U Bus Under Voltage 0.600 kV 0.561 93.4 3-Phase

Bus_UPS967X Bus Under Voltage 0.600 kV 0.562 93.7 3-Phase

Bus_UT957U Bus Under Voltage 0.600 kV 0.555 92.4 3-Phase

Bus_UT967X Bus Under Voltage 0.600 kV 0.559 93.2 3-Phase

Load-ATS953 Bus Under Voltage 0.600 kV 0.561 93.5 3-Phase

Load-ATS-963 Bus Under Voltage 0.600 kV 0.563 93.9 3-Phase

LVMCC-934E4 Bus Under Voltage 0.600 kV 0.559 93.1 3-Phase


LVMCC-954C1 Bus Under Voltage 0.600 kV 0.562 93.6 3-Phase

LVMCC-954C2 Bus Under Voltage 0.600 kV 0.562 93.6 3-Phase



LVMCC-964F Bus Under Voltage 0.600 kV 0.565 94.2 3-Phase

UPS-957U UPS Overload 0.064 Amp 0.069 107.0 3-Phase

UPS-967X UPS Overload 0.064 Amp 0.068 106.7 3-Phase

Utility-ATS953 Bus Under Voltage 0.600 kV 0.561 93.5 3-Phase

Utility-ATS-963 Bus Under Voltage 0.600 kV 0.563 93.9 3-Phase

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Appendix B: Short Circuit Analysis Results

Short Circuit Report (Utility Powered with CB-920A, CB-920B and CB-920TIE Closed)

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Short Circuit Report (Utility Powered with CB-920A & CB-920B Close, CB-920TIE Open)

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Short Circuit Report (Utility Powered with CB-920B & CB-920TIE Closed, CB-920-A Open)

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Short Circuit Report (Utility Powered with CB-920A &CB-920TIE Close, CB-920B Open)

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Short Circuit Report (DG-970 Generator Powered)

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APPENDIX C: Time Current Coordination analysis

Figure 1: ETAP System Model ...................................................................................... x



Figure 4: Time Current Coordination of CB-LVMCC934E-1 with Downstream CB-LVMCC934E-2 and CB-LT936 .................................. 67

Figure 5: Time Current Coordination of CB-LVMCC944E-1 with downstream CB-LVMCC944E-2 and CB-LT946 .................................. 68

Figure 6: Time Current Coordination for TR961F relay (Primary and Secondary) with downstream CBs including LVCC-964E3 (CB-HT983R) ......................................................................................... 69

Figure 7: Time Current Coordination for generator DG-970 with circuit breaker CB-DG970 ............................................................................... 70



Figure 10: Time Current Coordination for generator circuit breaker CB-DG970 with downstream CB-GEN-ATS963 and CB-HT983R ............. 73

Figure 11: Time Current Coordination for CB-DG970 with CB-LB979 ..................... 74

Figure 12: TCC for Protection of Motor M-250 with SR469 relay and FUSE-M3 ......................................................................................................... 75



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Figure 2: Time Current Coordination for TR951C relay (Primary and Secondary) with downstream CBs including LVMCC-934E4 (CB-LVMCC934E-1)

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Figure 3: Time Current Coordination for TR951C relay (Primary and Secondary) with downstream CBs including LVMCC-944E5 (CB-LVMCC944E-1)

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Figure 4: Time Current Coordination of CB-LVMCC934E-1 with Downstream CB-LVMCC934E-2 and CB-LT936

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Figure 5: Time Current Coordination of CB-LVMCC944E-1 with downstream CB-LVMCC944E-2 and CB-LT946

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Figure 6: Time Current Coordination for TR961F relay (Primary and Secondary) with downstream CBs including LVCC-964E3 (CB-HT983R)

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Figure 7: Time Current Coordination for generator DG-970 with circuit breaker CB-DG970

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Figure 8: Time Current Coordination for generator circuit breaker CB-DG970 with downstream CB-GEN-ATS953 and CB-LVMCC944E-1

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Figure 9: Time Current Coordination for generator circuit breaker CB-DG970 with downstream CB-GEN-ATS953 and CB-LVMCC934E-1

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Figure 10: Time Current Coordination for generator circuit breaker CB-DG970 with downstream CB-GEN-ATS963 and CB-HT983R

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Figure 11: Time Current Coordination for CB-DG970 with CB-LB979

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Figure 12: TCC for Protection of Motor M-250 with SR469 relay and FUSE-M3

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Figure 13: TCC for Protection of Motor M-230 with SR-469 Relay and FUSE-M2

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Figure 14: TCC for Protection of Motor M-210 with SR-469 Relay and FUSE-M1

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