Tank Type Ac Resonant Test System

Tank Type AC Resonant Test System

Introduction

TRST series tank type AC resonant test systems are designed for high capacitance load, special for XLPE power cables. There are variable frequency type (mainly used for XLPE cables field test) and variable inductance type (mainly for factory routine test).

TRST series tank type reactors are situated in an enclosed and earthed metal tank and filled with transformer insulation oil inside, additional voltage taps are possible, the output voltage is fed out through the tap-changers by HV bushings. These reactors extend application range, and satisfy testing for cables of various voltage classes.

Application

AC resonant test systems are mainly used to output AC voltage for high voltage routine, type and development testing of capacitive test objects. These systems exert the principle of series resonance, as per f=1/2LC, the connection of HV reactors (inductance L) to a capacitive loads (capacitance C) form an oscillating circuit with the frequency (f) of power supply.

Compared to conventional AC test transformers, the relatively lower power required (1/Q), smaller dimension and lighter weight favor these systems as the most practical for field testing, and large capacitance loads.

Configuration

Essential

Regulating transformer

Exciter transformer

HV reactor

Capacitor divider

Optional

Switchgear cabinet

Compensation reactor

Power line filter

HV filter

Principle

Series resonant circuit consists essentially of an inductor in series with a capacitive test object or load connected to a medium-voltage power source. Alternatively it may consist of a capacitor in series with an inductive test object. By varying the circuit parameters or the supply frequency, the circuit can be tuned to resonance, when a voltage considerably greater than that of the source and of substantially sinusoidal shape is applied to test object.

The stability of the resonance conditions and of the test voltage depends on the stability of the supply frequency and of the test system characteristic, described by the quality factor, which is the ratio between test reactive power and power loss.

When a discharge occurs, the circuit capacitance discharges instantaneously and then follow-through current from the source is relatively low. The limit follow-through current generally results in less damage to the test object.