Atec Biddle-27000 User Manual download pdf

PARTIAL DISCHARGE DETECTION SYSTEMS

BIDDLE



Series 27000

• Key component of all

Biddle partial discharge

detection systems

• Includes multiple

interference control

features

• Five built-in types

of data readout

• RS-232C interface for

control and data export

Partial Discharge (Corona) Detector

INTRODUCTION

ASTM defines a partial discharge as a

type of localized discharge that results

from transient gaseous ionization in

an insulation system when the voltage

stress exceeds a critical value. The

ionization is localized over only a por-

tion of the distance between the

electrodes of the system. The result-

ant partial discharge signals appear as

very small magnitude, fast-rise pulses

with irregular waveshapes superim-

posed on the high voltage at the

terminals of the test sample. Partial

discharges cause deterioration of in-

sulation materials and are a primary

cause of insulation failure at moderate

and high voltages.

The accepted unit for measurement of

partial discharge magnitude is the

picocoulomb. The picocoulomb, a unit

of charge, is columbs x 10

-12

. Charge is

preferred to voltage as a unit of mea-

sure because it is proportional to the

destructive energy released at the

discharge site. Pulse voltage is unde-

sirable because it is dependent on

partial discharge pulse waveshape

which is irregular at best.

Partial discharge pulse waveshape is

dependent on the location of the dis-

charge site and changes as the pulse

propagates through the circuit. The

charge, proportional to the number of

ions formed at the discharge site, is

represented by the area under the

partial discharge pulse waveshape.

This area remains constant, indepen-

dent of discharge site location. The

energy released is proportional to the

product of the number of ions formed

and the critical voltage at the dis-

charge site. It is therefore apparent

that the response from a properly de-

signed partial discharge detection

system must be proportional to the

area under the partial discharge pulse.

The Biddle



Partial Discharge Detec-

tion System integrates the area under

any partial discharge signals detected

and displays an output pulse-signal on

the oscilloscope which is proportional

in height to the integrated area. The

ratio of proportionality, in pico-

coulombs per unit of deflection, is

established by using the built-in cali-

bration equipment.

DESCRIPTION

The Biddle

Series 27000 Partial Dis-

charge (Corona) Detector is composed

of four functional units: the amplifier,

display, calibrator and evaluation unit.

Amplifier

The amplifier provides low-noise gain

and bandwidth limiting of the partial

discharge signals. The gain is continu-

ously variable over four decade ranges

and is determined by front-panel con-

trols. The input of the amplifier is

galvanically isolated from the source

of the signal to minimize grounding

problems and to provide protection

against common mode transients that

often occur during routine testing. Dif-

ferent partial discharge tests may

require amplifiers with different band-

width limiting. In these cases, the

detector can be equipped with two

amplifiers.

Display

The display circuitry includes partial

discharge pulse rectification and

brightening circuits, a display time

base and an electrostatic CRT display.

Pulse rectification is used to enhance

the clarity of the display and to make

the pulse polarity appear independent

of the phase of the test voltage.

The display time base provides a CRT

baseline upon which the partial dis-

charge pulses may be superimposed.

This baseline is phase-locked to either

the test voltage or detector line voltage,

providing a phase reference which is

essential for ac partial discharge pattern

recognition. The detector circuitry will

dynamically choose between these two

reference signals to see which

provides the more suitable phase refer-

ence. Front-panel indicators show which

phase reference signal is being used.

Three different baselines are available:

elliptical, linear and sinusoidal. Each

of the baselines is synthesized from

phase-locked-loop circuitry so that

test-voltage harmonics are completely

suppressed and do not appear on the

AVO INTERNATIONAL

BRINGING RELIABILITY TO AMPS • VOLTS • OHMS

1 2 3 4 5

Summary of Contents

Page 1 - Series 27000

PARTIAL DISCHARGE DETECTION SYSTEMSBIDDLESeries 27000• Key component of allBiddle partial dischargedetection systems• Includes multipleinterference c

Page 2

PARTIAL DISCHARGE DETECTION SYSTEMSSince partial discharge is often maskedby noise, internal digital filters may beused to minimize false trips, and t

Page 3

PARTIAL DISCHARGE DETECTION SYSTEMSPower Separation FilterU ~~U ~BushingBushingTapCouplerU ~BridgeCouplingUnitORORAPPLICATIONSThe keystone of all part

Page 4 - 123 456789101112131415

PARTIAL DISCHARGE DETECTION SYSTEMS7. Automatic scope display synchro-nization indicators8. Calibrator controls and indicators9. LCD partial discharge

PARTIAL DISCHARGE DETECTION SYSTEMSPulse Rise TimeLess than 100 ns (10 to 90%)Pulse Repetition Rate: Once per half-cycle of the test voltageRepetition

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Atec Biddle-27000 User Manual

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