Doble Solutions for Partial Discharge

Greg Topjian

Solutions Manager

617-393-3129

gtopjian@doble.com

Why do we need to conduct PD

measurements

• PD a major cause of early failure for HV insulation.

Partial Discharge

• PD is a symptom of degradation.

• Once present – it dominates as it’s own “inherent” stress degradation mechanism

• Its an early waning signal and precursor to complete insulation failure and breakdown

• PD diagnostics can be used to trend changes in the level and severity of insulation degradation

• Early detection of PD is critical in the prevention of in catastrophic failures

What Does PD Depend On?

• Electrical field stress

• Environment conditions - Temp and humidity

• Load or current

• Mechanical vibration

Important to have early stage of detection for PD

PD diagnostics: Used to trend changes in level and severity of the degradation of equipment installation

Partial Discharge

• Causes of PD in insulation system: – Voids in epoxy resins, polymers, paper

– Bubbles in liquids/oils

– Metal deposits, irregularities such as protrusions, contaminants

– Electrodes and insulation surfaces and interfaces

• Can arise through: – Poor design and manufacture

– Damage of equipment e.g. Transport damage

– Poor installation processes – poor workmanship

– General “ageing” or deterioration of materials

Why is Testing and Monitoring for PD Important?

Why is Testing and Monitoring for PD Important?

Why is Testing and Monitoring for PD Important?

Why Is testing and monitoring for PD Important?

9

Doble’s 4-Phased PD Products

Phase 1

Survey Instrument (PDS

100 and DFA) 100)

Phase 4

Permanent Monitoring

(Guard-Family)

Phase 2

PD-Smart

Testing

Phase 3

LDA6

Acoustic Locator

(Transformers Only)

PD Alignment with Doble Services

Four phases: Services wrapped into Phase 2-4

• Phase 1: Surveying

• Phase 2: Testing on- or off-line

• Phase 3: Investigative methods

• Phase 4: Permanent monitoring

• Phase 5: Doble Service Agreement (DSA)

• Includes electrical and UHF capabilities combined into one unit that will test PD on:

– Transformers

– Rotating machines (RM)

– MV/HV cables

– GIS

– And MORE!

PD-Smart Combine System

PD-Guard Monitoring System

• Key features:

– Advanced signal processing

– Interference suppressions

– Analysis software

• Continuously monitors your critical assets

• Most important: Automatic alarm system based on changes in activity rates rather than maximum values; this avoids false alarms due to one-time “outliers”

An important part of a thorough condition-

based maintenance program

Activity Rate Changes

• Monitoring changes in activity rates rather than maximum values avoids false alarms.

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PD Key Markets

Testing

Rotating Machines

(Motors & Generators)

PD of Rotating Machines

Rotating Machines Testing/Monitoring

Periodic testing

with PD-Smart

Permanent

monitoring with

PD-Guard

+

Sensor + Connection

Box

System Components

• Permanent PD testing with PD-Smart on machines

• Permanent PD monitoring on machines

System Components N

eutr

al

Bus Work Motor or

Generator

A

B

C

PD Evaluation Server

Analysis Software Calibrator

PD-Guard

Coupling Capacitors &

Installation Kits

Fiber

Optic

LAN

+

Inductive Sensor

Pulse Disturbance Gate

System Components

• PD-Guard

• 3-4 PDDC-24 or PDDC-17

• Calibrator

• Doble PD Support

IEC60270: Frequency is important!

• Doble Lemke uses 2nF coupler, whilst other suppliers using 80pF, 200pF coupler

• A coupler with a capacitance of 80F,200pF “sees” only the first part of the winding. Deeper Discharges / Slot Discharges will maybe not detected

• Coupler with 80pF, 200pF are not conform to the international standard as the measuring frequency is much higher as specified in the standard

PD Pulse vs. Location in RM

• Many generators have high frequency (HF) couplers installed with a strong high pass behavior, hampering PD measurement.

• HF couplers exhibit good performance for measuring PD close to it that is at the line end of the winding.

• They are worse than low frequency (LF) couplers for detecting PD in the middle and neutral end of the winding.

BC-Matching Unit (HF-Expander)

• PD-Measurement according to the standard of IEC60270 with a HF coupler

High Frequency

Coupler

+

BC-Matching

Unit

+

PD-Smart

PD Key Markets

Transformer Testing

Reasons for Testing and Monitoring

to Avoid…

UHF PD-Smart Testing

Pulse

Generator

LDC-7/UHF

Interfaces:

ActiveX Control

DCOM-Interface

M MODBUS

Ethernet Hub

Computer(s)

for Remote

Control &

Analysis

PD

Monitoring

Server

Software

LAN / WAN / Internet

PD-Guard/UHF

UHF Drain Valve

Sensors

UHF Plate Sensors

(Mounted in Hatch)

Fiber optic

LAN

Doble TransformerGuard

UHF PD-Guard Monitoring

PD Measurement on Transformers

Valve Connector Tank

Sensor Application

Measuring Impedance

• PD Measuring Impedance for Bushing Tap Installation

Doble Acoustic PD Locator: LDA-6 For Transformers Only

• Multi-channel acoustic transient recorder • 4 or 8 acoustical channel

• External triggering channel

– Intuitive PD location software

– Piezo-electric acoustic sensors & magnetic clamps

Comments Acoustics

• Acoustics are a valid technique for locating PD but it’s the wrong approach for detecting PD due to low sensitivity of the AE method and the fact that PD imbedded in the winding will not produce acoustic pressure waves detectable on the tank wall. So no Acoustic Signal does not mean no PD and detection via HF-CT on the star point end will only work for strong PD

Comments Acoustics (Cont’d)

• Some companies have convinced many Clients in our Region that Acoustic Measurements is detection of PD which is fundamentally wrong

• We obtain greater location accuracy using UHF triggering.

• Biggest Market for Location is probably service work

Acoustic PD Locator: LDA-6

Sensor 1

Sensor 4

Sensor 3

Sensor 2

1

Online Monitoring

PD Key Markets

Cable Testing

(on Site)

Terminations & Joints

1. Incorrect installation / poor workmanship

2. Manufacturing issues – poor QA

The Problems

Termination Aging Joint Weak Spot

• There is a wide range of possible problems in cable installations

• Apart from physical damage external defects in joints and terminations is the dominant cause of failure

• In addition some type and vintage of cables developed water treeing for various reasons but often related to outer sheath /jacket damage

• All of these problems may result in reduced life expectancy and premature failure of the cable

+

UHF Sensors + HFCT +

Connection box

PD-Smart:

For Periodic

Online testing

PD-Guard

For Online

monitoring

Cable Termination: PD-Smart/Guard

PD-Smart Cable Termination

HFCT

Cable Termination: PD-Smart/Guard

PD Key Markets

Switchgear Testing

(MV & GIS)

MV Switchgear Monitoring

• In MV switchgear often high humidity leading to surface tracking, material defects and incorrect assembly are responsible for PD activity

Schematic diagram of the PD-UHF-Monitoring-Setup at GIS by using UHF-Spacer-Sensor or internal sensor

PD sensor: spacer type frequency range: 100 MHz – 1200 MHz

Internal UHF sensor integrated in GIS

PD Smart -UHF

LDS6-UHF

Gas Insulated Switchgear (GIS) On-line

Doble’s PD Product Offerings

Phase 1

Survey Instrument (PDS

100 and DFA) 100)

Phase 4

Permanent Monitoring

(Guard-Family)

Phase 2

PD-Smart

Testing

Phase 3

LDA6

Acoustic Locator

(Transformers Only)

Questions?

Contact:

Greg Topjian

Solutions Manager

617-393-3129

gtopjian@doble.com