Perform voltage withstand test on 35kV/3km cable using a Variable Frequency AC Resonant Test System

　　1、Introduction

　　1.Implement preventive AC voltage withstand tests and handover AC voltage withstand tests for various test subjects;

　　2.Test the insulation resistance and capacitive load of tested items such as cross-linked rubber power cables,power transformers,GIS,transformers,insulators,generators,switches,etc

　　AC withstand voltage test.

　　2、Equipment combination

　　Subject:

　　Reactor 67.5kVA/27kV four section

　　Selection of 35kV/300mm2 cable 2km for excitation transformer output terminal

　　Using a reactor with two sections in series and two sets in parallel for a 5kV 10kV/300mm2 cable with a length of 5km

　　Using four sections of reactors in parallel for 1.5kV10kV switches and transformers

　　Use two reactors connected in series for 3kV

　　Rated capacity:270kVA;

　　Input power supply:single-phase 220 or three-phase 380V voltage,frequency 50Hz;

　　Rated voltage:27kV;54kV;

　　Rated current:10A;5A;

　　Working frequency:30-300Hz;

　　Device output waveform:sine wave

　　Waveform rate:Output voltage waveform rate≤1%;

　　Working time:Allow continuous 60 minutes under rated load;Overvoltage 1.1 times for 1 minute;

　　Temperature rise:After continuous operation for 60 minutes under rated load,the temperature rise is≤65K;

　　Quality factor:Q of the device itself≥30(f=45Hz);

　　Protection function:It provides overcurrent,overvoltage,and sample flashover protection for the tested product(see the variable frequency power supply section for details);

　　Measurement accuracy:System effective value 1.5 level;

　　One excitation transformer 15kVA/1.5/3kV/0.4kV

　　Rated capacity:15kVA;

　　Input voltage:0-400V,single-phase;

　　Output voltage:1.5/3kV

　　Structure:Dry type;

　　Weight:approximately 85kg;

　　1 variable frequency power supply 15kW/220/380V

　　Rated output capacity:15kW

　　Working power supply:220/380±10%V(single/three-phase),power frequency

　　Output voltage:0-400V,single-phase,

　　Rated input current:37.5A

　　Rated output current:37.5A

　　Voltage resolution:0.01kV

　　Voltage measurement accuracy:1.5%

　　Frequency adjustment range:30-300Hz

　　Frequency adjustment resolution:≤0.1Hz

　　Frequency stability:0.1%

　　Running time:continuous 60 minutes at rated capacity

　　Continuous operation for 60 minutes at rated capacity,high temperature of components≤65K;

　　Noise level:≤50dB

　　High voltage reactor 67.5kVA/27kV 4-section

　　Rated capacity:67.5kVA;

　　Rated voltage:27kV;

　　Rated current:2.5A;

　　Inductance:50H/single section;

　　Quality factor:Q≥30(f=45Hz);

　　Structure:Dry type;

　　Weight:approximately 65kg;

　　1 set of capacitive voltage divider 60kV/1500pF

　　Rated voltage:60kV;

　　High voltage capacity:1500pF

　　Dielectric loss:tgσ≤0.5%;

　　Partial pressure ratio:1000:1

　　Measurement accuracy:RMS level 1.5;

　　Weight:approximately 8kg;

　　The insulation structure of electrical equipment with high working voltage at power frequency in the 110kV cable withstand voltage test standard system must be able to withstand the high working voltage at power frequency for a long time during the entire operation process,usually referred to as the high working voltage of the system,which is generally 1.15 times the rated voltage.

　　When a circuit is connected in series with a resonant circuit,such as cutting off or closing a long no-load line,cutting off a no-load transformer(pneumatic variable),etc.This type of overvoltage waveform is very irregular and the situation varies greatly.It can be a attenuated oscillation wave or an aperiodic voltage shock wave,typically reaching a high voltage within 1ms.