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Introduction

• Micro TAPP voltage control and monitor is a numeric system based

• Widely used as Super TAPP relay• Operational control of Tap changing transformers and

protection against abnormal voltage• Full supervision and self monitoring of the internal

relay functions• User friendly access to the relay setting, displays

ontions and fault data• A Reydisp evolution software is used to set and

commission the relay.

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Power System Requirements• Power supply quantity in all voltage level from transmission and

distribution networks• Automatic voltage control of the electrical network is done by the use

of voltage sensing relays:- On Load Tap Changers (OLTC)Micro TAPP Functionality• An analog voltage and current are connected to the measurement

inputs• Quantities are filtered out for noise• Sampled 32 x per cycle at 50 Hz system and digitised• Use 3 phase VT, one phase is used for measurement. Phase A-B for

measurement and B-C phase for measurement monitoring.• Plant input such as “tap in progress and remote “tap raise or lower”

are connected to the status inputs• Intelligent operation monitoring by BCD (Binary Coded Decimal)

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• The VT input to the relay is measured against the target setting applied via the system menu

• The voltage is only used for measurement if the voltage quantity is confirmed as satisfactory by the voltage monitor

• The relay will respond to a voltage which is outside the set-point dead band and initiate a timing interval for operation of the transformer tap changing mechanism

• Where a 3 phase VT is used, each phase is monitored as a check against fuse failure

• Any abnormalities detected will inhibit the voltage raise outputs from the relay.

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Current Measurement

• The measurement of transformer is used by the relay to :-

a) Calculate the group connected load and provide network Load Drop Compensation (LDC)

b) Calculate circulating reactive current

c) Provide on-line reading and historic data

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• When selected to “automatic” mode:- the voltage regulating relay controls the transformer tap changer

• Voltages which are outside set voltage limits (dead bands) automatically initiate the operation of the transformer tap changer

• When selected to “manual” mode:- the voltage can be regulated via the relay manual raise/lower control switches

• The raise or lower command will only be issued after an initial time delay as set on the voltage regulating relay

• A definite time or an inversely time characteristic is selectable at Micro TAPP.

• Raise and Lower commands operate normally open relay contacts. Output contacts can be mapped to generate alarms or lockout signal

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Transformers in Parallel• With traditional schemes where 2 or more

transformers are connected in parallel• The following conditions are met:-

a) The transformers are identical

b) The transformers have the same number of taps and tapping interval

c) The transformers have the same impedance

d) The transformers are always on the same tap position

e) The transformers are fed from the same primary source

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• The Micro TAPP can be configured for use with Master/Follower tap change control scheme, but it is not recommended

• Each Micro TAPP can be connected to other Micro TAPP relays through a screened twisted paired cable

• The Micro TAPP Peer to Peer Communication (MPPC) system is used to transfer data between the relay at site

• If a Micro TAPP relay is de-energized, communication between other relays is not affected

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Relay Settings• The Micro TAPP is designed as an integral control device • The following information is used by the relay

a) Site data:- Number of transformer forming a groupb) Transformer data:- Rating, impedance, VT and CT detailc) Tap change:- Number of steps, type, etcd) Network data:- Power factor, system voltage, group capacity, etce) Voltage control:- Basic, Band, LDC, etc

• Micro TAPP relay can be configured as ‘Transformer switch out’ and ‘Transformer switch in’

• The command can be initiated either by a SCADA signal from a PC via communications network or from hard wired lacal control switch

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Control• Micro TAPP relay provides both manual and automatic control of the

tap changing system• The relay is configurable for either local control or remote control

from a control center• Electrical control of a tap change mechanism is normally exercised

from 3 point:-a) At the tap change mechanism:- A Local/Remote selector switch at the

tap changerb) At the voltage control relay panel:- Local/Remote selector on the Micro

TAPPc) At a remote site:- When Micro TAPP is set to Remote, control can be

selected and operated from a remote control center• Auto/Manual:- This switch sets the relay to automatic or manual

voltage control• When the Micro TAPP is set to “manual”, the relay will not correct

the voltage automatically

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• Raise/Lower:- When the Auto/Manual is set to manual, this switch allows the tap changer to be operated either to increase the tap position or reduce the tap position

• Tap changer:- The tap changer operation is monitored for a mechanism wiring or relay fault. The following is provided

a) Tap change run awayb) Tap change incompletec) Limit of tap change ranged) Tap not achievable

• For correct operation, the following must take place:a) A control signal must be issued to initiate the processb) The tap position must change to a new positionc) The tap change mechanism must stop completely

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• Fault records:- This screen enables the 10 most recent tap changer fault to be viewed. For each with date and time stamped.

• Event Records:- The event storage buffer holds 200 records with date and time stamped

• A green LED labeled ‘Relay Healthy’ is provided and will be permanently ON. If a permanent fault is detected the LED will flash continuously

• A green LED indicates that the measured voltage is normal• A red LED indicated that the measured voltage is above the relay

dead band setting. If the over-voltage monitor has detected a failure the LED will flash

• A red LED indicates that the measured voltage is below the relay dead band setting. If the under-voltage monitor has detected a failure, the LED will flash

• An amber LED indicates that the tap change mechanism is in the operating state. If the tap change monitor has detected a failure, the LED will flash

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• Micro TAPP relays are housed in either Epsilon E8 or E12 case

a) E8 case (MT 101) 11 input and 5 outputb) E12 case (MT 102 or MT 101 with extra I/O) 19 input and 13 output

• Rear case an IRIG-B port is also provided for time synchronization

• 2 pairs of fiber optic ST plug connectors are available for the following ;

a) Com1 for substation SCADAb) Com2 for access by protection engineer to the relay from a laptop

computer or PC using sigma converter

• Front 25 pin RS232 port is also available• For IEC 103 protocol should operate on either com1 or com2

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Power System Voltage Control

MicroTapp

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BUSINESS REQUIREMENTS

• CUSTOMER

• Correct voltage levels at all times

• Continuous supply

• SUPPLIER

• Zero Maintenance

• Zero Adjustments for any operational situation

• Minimisation of system losses

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OPERATIONAL PROBLEMS

• Network switching

– Switching transformers OUT of service

– Switching transformers IN to service

– Networks in parallel

• Automated control systems

• Embedded Generation

• Skill levels

• Abnormal voltages

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TAP CHANGE CONTROL SYSTEMS

• MASTER - FOLLOWER– COMPLEX CONTROL SYSTEM– TRANSFORMERS & TAP CHANGERS MUST BE IDENTICAL– INCOMING VOLTAGES MUST BE THE SAME– NOT ABLE TO RUN IN PARALLEL ACROSS A NETWORK

• CHANGE-OVER SCHEMES– SHORT OUTAGE DURING CHANGE-OVER– COMPLEX CONTROL SYSTEM– INCREASED COPPER LOSSES

• CIRCULATING CURRENT– SIMPLE WIRING BUT REQUIRES CB AUXILLARY SWITCHES

– NOT ABLE TO RUN IN PARALLEL ACROSS A NETWORK• REACTIVE CIRCULATING CURRENT

– SIMPLE WIRING– PARALLEL OPERATION ACROSS A NETWORK– CAN OPERATE DISIMILAR TRANSFORMERS IN PARALLEL

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‘Identical’ Transformers

Line Voltage (kV)

11

11.1

11.2

11.3

Current (A)

0

250

500

750

1000

Power Factor

0.7

0.8

0.9

1

Tap Position

1

2

3

4

5

6

Circulating Current (A)

0

20

40

60

0:00 6:00 12:00 18:00 0:00

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Parallel Transformers

'High' 'Low'

‘Transformers are on the correct tap position when minimum circulating current flows between them and the system voltage is correct’

Reactive current flowbetween transformers

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Reactive Current

Line Voltage

Load

Export circulatingcurrent

Measured voltage

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MicroTAPP - True Circulating Current

Voltage

G roup Load

T 1 current

C irculating

current

T 2 current

T 1

T 2

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Reactive Circulating Current

T arget PF

Voltage

G roup Load

T 1 current

C irculating

current

T 2 current

T 1

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7 8 9 9 7 7 7 6

Tx A

Tap > Tap >

Tx B

A BA B CC

Conventional AVR – Why Independent Auto Results in Drifts

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7 8 8 7 7 7 8 8

Tx A

Tap > Tap >

Tx B

A

B

A B

CC

Microtapp – Independent Auto, but No Drifts

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Features

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Initial Delay to tap Change - DMT

O perateT im e

RelayDeadband

80% Volts

Initia lDelay

Band+2%

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Tap Change - Overcurrent Blocking

Voltage

T ransform erLoad

Full Load

Norm al O peration

Block Raise Volts

B lock Low er Vo lts

T otal b locking

80% Volts

Low er Band

Upper BandBlocks operationfor excessive LOADbut allowsoperation to reduceCIRCULATINGcurrent

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Tap Change - Normal operation

time

Raise / Lower Reclaim pulse time

Raise / Lower Reclaim pulse time

Normal Raise / Lower command

In progress logic

Intelligent Tap Positionindicator

Lock out

IP Indication

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Tap Change - Runaway condition

time

Raise / Lower Reclaim pulse time

NOTE: Timed lockout will occur if second TPI is NOT detected

Normal Raise / Lower command

In progress

Intelligent Tap Positionindicator

Lock out

Timed tap change lockout

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Hardware

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MicroTAPP - E8 Case General View

RELAY HEALTHY

LO W

NO RM AL

HIG H

T AP INPRO G RESS

TRANSFO RM ER 1

10.9 07kV -1h

LO CAL AUTO

TAPCO NTRO L

M ENU TEST LEDS

T AP

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MicroTAPP - Rear View Connections

IR IG B

T X1

RX1

T X2

RX2

28 W AY CO NNECT O RBLO CKS

REAL T IM E CLO CKINPUT

CO M M UNICAT IO NSPO RT 1

CO M M UNICAT IO NSPO RT 2

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MicroTAPP - Operational Display

TRANSFO RM ER 1

10.9 07kV -1h

LO CAL AUTO

TAPCO NTRO L

M ENU TEST LEDS

T AP

TRANSFO RM ER 1

10.9 07kV

LO CAL AUTO

TAPCO NTRO L

M ENU TEST LEDS

T AP

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MicroTAPP - Control Level Display

LO W ER RAISE LO CAL REM O TE

EXITAUTO /

M ANUALM O VE ->

M ANUAL/AUTO

TAP 711.2kV

LO W ER RAISE LO CAL REM O TE

LO W ERTAP

RAISETAP

M O VE ->

M ANUAL/AUTO

TAP 711.2kV

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MicroTAPP - Configuration

TRANSFO RM ER 1

UP DO W N SELECT

SETTING S M O DE

INSTRUM ENTS M O DE

FAULT DATA M O DE

20/09/1999 16:08:40

CANCEL

TRANSFORMER 1

EXIT NEXT CANCEL

20/09/1999 16:08:40

11.3 18.0 0.97Line (kV) Load (MVA) pf lag

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Settings

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24 hour Historical Records

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Event Listing

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VT and CT Connections

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Connection to Tap Position Transmitter

Resistor Chain Type BCD Type

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MPPC Screend twistedpair cable

MPPC line terminatorlink

MPPC line terminatorlink

MPPC screen earthing ata single point

MPPC Inter-MicroTAPP connections

MicroTAPP 1

B1B3 B5

B7

IntermediateMicroTAPP

B1B3 B5

B7

MicroTAPP N

B1 B3B5

B7

MPPC Link Connection

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Communications

Communications to IEC60870-5-103 protocol

Fibre optic with ST connectors

May be connected in a loop with 254 relays

Fibre optic hub available for star configuration

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Ring Connected Data Comms

F.O Cables

Sigma3

TXRX

RX

RXRXRX

TX

TX TX TX

RS232

PCs to be equipped with Reydisp software

Up to 254 relays can be connected in single loop

Each relay to have unique address LocalPC

RemotePC

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Star Connected Data Comms

• Star connected data comms• Increased Security

• Sigma 1 F.O. Hub

F.O Cables

Sigma1

LocalPC

RemotePC

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MicroTAPP - A complete system

Basic Voltage Control Relay

Monitor Relay

Local / Supervisory Control Switching

Communications

Tap Position Inputs

In service over 14 yearsSuperTAPP >6000MicroTAPP >400