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CHAPTER 6HIGH VOLTAGE GENERATION,

MEASUREMENT AND TESTING TECHNIQUE

byAssoc. Prof. Dr. Mohd Muhridza YaacobInstitute of High Voltage & High Current

Faculty of Electrical EngineeringUniversiti Teknologi Malaysia

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Introduction

Generation of high voltage and current are required for testing of power equipment Simulating the stresses on the insulation

to overvoltages to determine the insulation strengthVoltage stresses such as the power

frequency and high frequency voltages, lightning impulse, and switching impulse.

Introduction In high voltage testing, the current under

failure conditions is limited to small value (less than 1 A for d.c. or a.c. voltages and few amperes for impulse or transient voltages).

High currents are required when testing surge arresters or short-circuit testing of switchgear (several kA)

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Classification1. High Voltage Direct Current

(HVDC)2. High Voltage Alternating Current

(HVAC) 3. High Impulse Voltage Lightning

& Switching4. High Current AC, DC & Impulse

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HVDC Generation Required for insulation testing on

cables and capacitors Used also as impulse generator

charging unit Generation circuits are;1. Half Wave and Full Wave Rectifier2. Voltage Multiplier Circuits3. Voltage Doubler Circuits

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HVDC Generation

1. Electron Tube rectifier up to 250 kV

Solid state or semiconductor rectifier up to 20 kV. For higher voltage several units are used in series

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HVDC GenerationIn modern high voltage lab semiconductor (solid state) rectifier stacks are usedCommonly prefered are silicon diodes with PIV of 1 to 2 kV or selenium element with PIV up to 500 V

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HVDC GenerationHalf Wave Rectifier

+ve half-cycle: C is charged to Vmax-ve half-cycle: C is discharged to loadCRL = 10 times the ac supply periodRectifier valve have peak rating of 2VmaxR is connected in series with transformer output to limit current

HVDC Generation

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Output Without smoothing C

Output Withsmoothing C

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HVDC Generation

Full Wave Rectifier+ half-cycle: A conducts

and charged up C (smoothing capacitor)

-ve half-cycle: B conducts and charged up C Centre-tap source transformer of 2V

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HVDC Generation(a) Sine wave input(b) Output of half-wave(c) Output of full-wave V is the fluctuation

in output dc duringon-load (ripple)

V is larger for half-wave Ripple is kept low by

proper choice ofcapacitor and transformer reactance

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TransformerRectifier

HV Arm Resistive DividerLV Arm

Ground

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HVDC Control Panel

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HVDC GenerationVoltage Doubler Circuit - C1 is charged through

R1 to Vmax (-ve cycle)- transformer voltage rise to Vmax and C1potential rises to 2Vmax(+ve cycle)

- C2 in turn charged to 2Vmax thro R2

- Cascaded voltagedoubler for larger output voltage

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HVDC GenerationVoltage Multiplier Circuits (Cockcroft-

Walton) 1st stage same as

doubler circuit (D1,D2,C1,C2)

For higher voltage the circuit is repeated with cascade or series connection (4,6,..2n)

C4 charged to 4Vmax and C2n to 2nVmax

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HVDC GenerationD1,D3,D2n-1 conduct during +ve half-cyclesD2,D4,D2n conduct during -ve half-cyclesVC2 = Vac + VC1The voltage across othercapacitors (C2 C2n) is the difference between voltage across theprevious capacitor and charging voltage

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HVDC Measurement

Essential to measure voltage & current accurately to ensure safety to personnel and equipment

Method or technique;1. Series resistance microammeter2. Resistance potential divider3. Generating voltmeter4. Sphere and other spark gap

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HVDC Measurement

High Ohmic Series Resistance with Microammeter

- A very high resistance (hundreds of M) connected in series with microammeter

Vsource = IR - Voltage drop in meter is

negligible since meter impedance is small

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HVDC Measurement

- Protective device as protection against high voltage if R fails

- Resistor constructed from wire wound

- Ohmic resistor value is chosen such that 1 10 A is allowed for full scale defelction

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HVDC MeasurementLimitations:1. Power dissipation and source loading2. Temperature effect and long time stability3. Voltage dependence of resistive elements4. Sensitivity to mechanical stress

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HVDC Measurement

Resistance Potential Divider

Resistance connected to electrostatic or high impedance voltmeter

High voltage magnitude

= [(R1 + R2)/R2]V2

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HVDC Measurement

Generating VoltmetersA variable capacitor electrostatic

voltage generator which generates current proportional to the applied voltage

No direct connection to high voltage electrode

eg. Van de Graaff Generator

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HVAC Generation

- Single transformer for voltage < 300 kV

- Used for routine test of service equipment such as transformers, switchgears and cables

- Cascade & Resonant Transformers

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HVAC GenerationCascade Transformer

- 1st Tx. at ground potential- 2nd Tx. kept on insulators

and maintained at V2- HV winding of 1st unit

connected to tank of 2ndunit

- LV winding of 2nd unit is supplied from excitation winding of 1st unit

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- 3nd Tx. kept on insulators above ground at ground potential of 2V2 and is supplied from the 2ndunit.

- Supply 230 400 V for up to 100 kVA

- Supply 3.3 11 kV for larger units

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- 2nd scheme using isolating transformer (IS1, IS2, IS3) to excite 2nd& 3rd stage and are insulated to tank potentials

- Supply from same ac input

- Expensive , spacing but natural cooling, light & compact

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- Testing of hv apparatus involves supplying of capacitive loads with low power dissipation

- Transformer Rating, P = kV2C (k>1.0)k to account extra capacitanceV nominal output voltage of TxC test object capacitance - angular frequency

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HVAC Generation

Cascade Transformer- Typical Capacitance values of test object;

Test Object CapacitanceP. Tx (< 1 MVA) 1000 pF

(> 1 MVA) 1000 10 000 pFP. Cables (solid) 250 300 pF/m

(gas) 50 80 pF/mGIS s/station 100 10 000 pF

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HVAC GenerationResonant Transformer- Eqv. Cct: windings leakage

reactance & resistance, magnetizing reactance and shunt capacitance across the output terminal due to bushing of hv terminal and test object

- Utilised in testing at very high voltage and on occasion requiring large current such as cable test, dielectric loss and pd measurement

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HVAC GenerationSeries Resonant Transformer

To have series resonance at power frequency, L1 + L2 = 1/CVc = -jVXc/[R + j(XL-XC)]

= VXC/R = V/CRThe factor XC/R is the Q factor which gives the magnitude of the voltage multiplication across the test object under resonanceTest Condition; (Le + L) = 1/ C

Le eqv. Leakage inductance

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HVAC GenerationParallel ResonantHv reactor connected asauto transformerMore stable output andhigh rate of rise of testvoltageBuilt for 500 kV single unitCascaded unit for 3000kV

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HVAC GenerationPrinciple of operation- Voltage regulator (auto-transf or induction

reg.) is connected to main supply- 2ndary winding at exciter transf. is connected

across hv reactor L & C- Inductance of reactor is varied by varying air

gap- C is the test object, divider, bushing

capacitances- Q factor = 50

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HVAC GenerationAdvantages;1. Pure output sine wave2. Less power requirement3. No high-power arcing and high current surges

if test object fails as resonance ceases at failure4. Possible for cascading5. Simple & compact6. No repeated flashoverDisadv. requirements of additional variable

chokes

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HVAC Measurement

1. Series Impedance Voltmeter2. Series Capacitance Voltmeter3. Capacitance Potential Divider4. Voltage Transformer5. Electrostatic Voltmeter6. Peak Reading AC Voltmeter7. Spark Gap

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HVAC MeasurementSeries Impedance Voltmeter

- for power frequency by using pure resistance or reactance- capacitor often used as series reactance sinceresistance involves power loss problem in variation of resistance with temperature

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HVAC Measurement

Series Impedance Voltmeter -residual inductance of the

resistance give rise to impedance which is different from its ohmic value

- Z = R + jL(1 - 2LC) + j CR)

= R[1 + j(L/R - CR)]

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HVAC MeasurementSeries Capacitance

VoltmeterIc = jCVV = (V12 + V22 + ..+Vn2)- not recommended when

ac voltages are not purely sinusoidal but contains harmonics

- used with cascade transf. For measuring rms up to 1 MV

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HVAC Measurement

Series Capacitance Voltmeter

- series capacitance formed as a parallel plate capacitor between hv terminal and ground plate

- rectifier ammeter as indicating instrument and directly calibrated in hv rms value ( 0 100 A)

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HVAC MeasurementCapacitance Voltage Divider

- eliminate errors due to harmonic voltages

- C1 : Std compressed air or gas capacitor as C1

- C2 : large capacitor (mica @ paper)

- C1 is connected to C2 thro shielded cable

- C2 is completely shielded in a box to avoid stray capacitances

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HVAC MeasurementCapacitance Voltage Divider

V1 = V2 C1 + C2 + CmC1

Cm capacitor of the meter & connecting cableV2 meter reading

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HVAC Measurement

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HVAC Measurement Capacitance Voltage

Transformer (CVT)- Capacitance divider with suitable matching or isolating potential transformer tuned for resonance condition- C1 made up of few units of hvcapacitors - Transf. ratio : hv:10 to 30 kV,

lv:100 to 500 V- Value of L (tuning choke) is chosen to make eqv. cct. of CVT purely resistive

(L + LT) = 1/(C1 + C2)

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HVAC MeasurementCapacitance Voltage Transformer (CVT)Advantage;- Simple design and easy installation- Frequency independent- Used as voltage measuring device for coupling

condenser- Provides isolation between hv terminal dan lv meterDisadvantage;- Voltage ratio is susceptible to temperature variation- Ferro-resonance

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HVAC Measurement

CT/PT

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HVAC MeasurementElectrostatic Voltmeter- Made with parallel plateconfiguration using guardring to avoid corona- Force on the plate measured by controlling it by a spring or balancing with counter weight- Small displacement of the electrode is sufficientfor voltage measurement

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HVAC MeasurementPeak Reading AC Voltmeter- To obtain the maximum dielectric strength of insulating solids- Rd permit variation of Vm when V2 is reduced- Cs charged to peak value to be measured by C2- CsRd is 1 to 10 s

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HVAC Measurement

Sphere Gap

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HVAC Measurement- Uniform field spark gap have a sparkover

voltage within a known tolerance- Can measure peak value of voltage if gap

distance is known- Vs = 30 kV peak at 1 cm spacing in air at

20C and 760 torr- Arrangement : vertically with lower gap

grounded or horizontally

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HVAC Measurement

- Rseries connected between source and gap to limit Ib/d and suppress unwanted oscillations in the source voltage when b/d occurs

- Factors affecting sparkover voltage of gap:1. Nearby earthed objects2. Atmospheric conditions & humidity3. Irradiation4. Polarity & rise time of voltage waveforms

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HVAC Measurement

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HVAC Measurement

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HVAC Measurement

High Voltage ProbeHigh Voltage Divider Dr. MMY 2012

Impulse Voltage Generation & Measurement

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Impulse voltages are required in high-voltage tests to simulatethe stresses due to external and internal overvoltages,

They are generated by discharging high voltage capacitorsthrough switching gaps onto a network of resistors andcapacitors

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Generation of Impulse VoltageWaveform to be generated - Risetime of 0.5 to 10 s, Decay time 30 to

200 s - Unidirectional & double exponential;

v(t) = V0[exp(-t) exp(-t)] where, & time constant

- The equation represents a wave with rapid rise to peak and slowly falls to zero

- During waveshape recording the initial portion may not clearly defined or missing due to disturbances

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Generation of Impulse Voltagetf or t1 = 1.25(t90 t10) 30%tt or t2 = T3 20%Std. Waveshape = 1.2/50 s

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Generation of Impulse Voltage Circuit to produce impulse wave Series R-L-C under overdamped or R-C

combination. C is charged to a particular dc voltage and discharged thro waveshaping network. Rd and Re control the front and tail time

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Generation of Impulse Voltage

Circuit Analysis of Impulse GeneratorCircuit (a); Vo(t) = Vc [exp(-t) exp(-t)]

R1C2( - )Circuit (b); Vo(t) = VcC1R2 [exp(-t) exp(-t)]

( - )where;

= 1/(R1C2) and = 1/(R2C1)

Vo(t) - output voltageVc - charging voltage

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Calculation of front time and tail time;

t1 = 3R1 C1C2 = 3R1CeC1 + C2

t2 = 0.7(R1 + R2)(C1 + C2)

Energy rating of generator = C1V02

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Multi-stage Impulse Generator is used to generate higher impulse voltage output

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Multi-stage Impulse Generator

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Multi-stage Impulse Generator

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Components of Multistage IG1. DC Charging Set2. Charging Resistor3. Charging Capacitors4. Spark Gaps5. Waveshaping Resistors6. Voltage Dividers

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Corona Rings

Dividers

Chopping Gap

Impulse Generator

Impulse Generator Output

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Impulse Generator Output

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Measurement of Impulse Voltage

1. Potential Dividers Either resistive,

capacitive or mixed element type

Low voltage arm is connected to fast recording oscillograph or peak reading intsrument

Z1 & Z2 series resistors or capacitors

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Measurement of Impulse Voltage Errors and distortion in output waveshape due

to: 1. Residual inductance in the elements 2. Stray capacitance between element, elements terminal to ground, high voltage lead to element 3. Impedance errors due to connecting leads between dividers and test object and ground return leads 4. Parasitic oscillations due to lead and cable inductances and capacitance

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Measurement of Impulse Voltage

2. Sphere Gap

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Multiple Impulse Generator (MIGe)

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MIGe Achievements

1. 1. Silver Medal at INATEX 20082. 2. Silver Medal at Malaysia Technology Exposition

(MTE) 20083. 3. Gold Medal at Seoul Int. Invention Fair 20084. 4. Special Award at Seoul Int. Invention Fair 20085. 5. Patent Filing PI 2008 12726. 6. Nine Technical Journal and Conference papers7. 7. One monograph and one book chapter8. 8. One PhD and nine Master tesis9. 9. Nominated for Anugerah Harta Intelek Negara 2009

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EXAMPLE 1An impulse generator has been designed to generate an impulse voltage of 1.2/200 s waveshape. Find the waveshaping resistors R1 and R2 when C1 = 0.125 F and C2 = 1 nF.

Soln.tf = 3R1 [C1C2/(C1 + C2)] 1.2 x 10-6 = 3R1 [(0.125 x 10-6 x 1 x 10-9)/ (0.125 x 10-6 + 1 x 10-9)] R1 = 400

tt = 0.7(R1 + R2)(C1 + C2)200 x 10-6 = 0.7(R1 + R2)(0.125 x 10-6 + 1 x 10-9) R2 = 1868

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EXAMPLE 2An impulse generator having charging capacitor of 0.01 F. The wave front and wave tail resistances connected are 800 and 5000 respectively. If the load capacitor is 1000 pF, find the front and tail times of the impulse wave produced. Comment on the answer as compared to the standard waveshape of 1.2/50 s.

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Soln.tf = 3R1 [C1C2/(C1 + C2)]

= 3 x 800[0.01 x 10-6 x 0.001 x 10-6][0.01 x 10-6 + 0.001 x 10-6]

tf = 2.19 s

tt = 0.7(R1 + R2)(C1 + C2)= 0.7(800 + 5000)(0.01 x 10-6 + 0.001 x 10-6)

tt = 46.7 s

Front time is outside the range of 1.2 s 30% (0.84 to 1.56 s)

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EXAMPLE 3A ten stage impulse generator have C1 = 0.2 F per stage and an external load capacitor C2 = 1 nF. Determine the values of waveshaping resistors at each stage to generate standard lightning impulse of 1.2/50 s waveshape. If the DC charging voltage is 100 kV, determine also the output voltage and generator energy rating.

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Soln.n = 10, thus for 10 stage; nV0 = 10 x 100 kV = 1000 kV, C1/n = 0.02 F, C2 = 1 nF, front resistor = 10R1, tail

resistor = 10R2tf = 3R1 [C1C2/(C1 + C2)]

1.2 s = 3 x (10R1) [0.02 x 10-6 x 1 x 10-9][0.02 x 10-6 + 1 x 10-9]

R1 = 42

tt = 0.7(R1 + R2)(C1 + C2)50 s = 0.7 x 10(42 + R2)(0.02 x 10-6 + 1 x 10-9)

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1. INTRODUCTION

Purpose of the testing: To ensure that the electricalequipments are capable of withstanding the overvoltagesthat are met with in service.

Covers basic requirements procedures for testing on severalelectrical apparatus. Normally, high voltage (HV) testing is toinvestigate the insulation performance.

International/national specifications for testing are outlined(details of test, specific equipment, procedure andacceptable limits) to meet the users and manufacturersrequirements

HIGH VOLTAGE TESTING TECHNIQUESHIGH VOLTAGE TESTING TECHNIQUES

IVATIVATUTMUTM

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2.1 CLASSIFICATION OF HIGH VOLTAGE TESTS

Destructive Test

Normally the equipment underwent destructive test cannot beused in the service.

Test voltage is higher than its normal working voltage.

Breakdown test.

Non-Destructive Test

Mainly done to assess the electrical properties, eg. Resistivity,dielectric constant and loss factor.

The apparatus is not destroyed during the test and can be usedagain


IVATIVATUTMUTM

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2.2 TYPES OF TESTS

Routine Tests

Made by the manufacturer on every finished piece ofproduct.

To fulfills the specifications

Type Tests

Performed on each type of equipment before their supplyon a general commercial scale demonstrateperformance characteristics.

No need to repeat the test unless changes are made inthe design of the product.


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TYPES OF TESTS (Cont.)

Special Test other than routine or type

Maintenance Tests

Usually carried out after maintenance/repair ofthe equipment.

Conducted according to schedule provided.

Purpose of the test : To ensure the equipmentlifetime is achieved.


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3. TEST VOLTAGES

Can be divided into three, eg. Direct voltages (DC),power-frequency alternating voltages (AC) andimpulse voltages.

Test with Direct Voltage (DC).Mainly to test equipment used in HVDC transmission systems.Insulation testing, fundamental investigations in discharge physics and dielectric behaviour. Rate of voltage rise above 75% of its estimated final value should be about 2% per second.


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TEST VOLTAGES (Cont.)

Test with Alternating Voltage (AC).

Frequency range : 40-60 Hz, sinusoidal shape.

Dry withstand test : Most common routine test for alltypes of electrical equipment especially insulators,bushing, rod gaps etc.

Applied voltage between two to three times of the normalworking voltage.

Wet withstand test : To simulate the effect of natural rainon external insulation. Recommended for tests onapparatus which are designed for outdoor used.Useartificial rain.Applied for 30-60 seconds.


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Test with Impulse Voltage. Is designed to investigate

the insulation performancedue to the lightning strokeor switching operation.

3 types of impulse voltages,ie;

1) Full wave

2) Chopped wave

3) Switching wave

BS 923: Part 2: 1980

Full lightning impulse

Lightning impulse choppedon the front

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IVATIVATIVATUTMUTM

Lightning impulse choppedon the tail

Full switching impulse

BS 923: Part 2: 1980

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Rated impulse withstand test

For test on non-self-restoring insulation, 3 impulses areapplied.

For withstand tests on self-restoring insulation, 2 proceduresare use:

1) 15 impulses (rated withstand voltage) with the specifiedshape and polarity are applied

2) Test procedure for determining 50% disruptive dischargevoltage is applied

The method used for determining the levels of appliedvoltage is up-and-down methods.

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Atmospheric Correction Factors

By applying correction factors, a measured flashover voltage that influenced by the atmospheric conditions can be determined.

Tpk

kkkVV

d

o

273293

760

by,given ,density air offunction a is where d

kd 0.70 0.75 0.80 0.85 0.90 0.95 1.0 1.05 1.10 1.15

k 0.72 0.77 0.82 0.86 0.91 0.95 1.0 1.05 1.09 1.12

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4.0 DIAGNOSTIC TESTING OF INSULATION

The purpose of diagnostic testing is to estimate the importance of any deterioration.

Diagnostic testing can use measurements of;

Non-electrical properties

Breakdown strength

Conductivity/Resistivity

Loss tangent

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IVATIVATIVATUTMUTM

Loss Tangent (tan )

Figure 1.1

V

I

I

V

I

VRp Cp

IR IC ICI

IRV

Figure 1.2 : Parallel model

tan = I I

R

C tan =

V / RV C

p

p

tan = 1

C Rp p

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I

VR

VC

Rs

Cs

V

VR

VC

I

V

Figure 1.3: Series model

R = R

1 + C Rsp

2p2

p2

C = C + 1C Rs p 2 p p2

tan = V V

= I R

I 1C

R

C

s

s

tan = CsRs

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Measurement of tan (dissipation factor), resistance and capacitance ofthe sample are often made using a.c. bridges.

The common bridge circuits used in power frequency high voltages are:

Schering Bridge

Transformer ratio-arm

AC

A

BD

C

detector

Z1 Z2

Z3 Z4

Figure 2.1

At balanced condition

Z1 Z4 = Z2 Z3

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The Schering Bridge

AC

C

r

R3

C2

R4 C4

Figure 2.2: Schering Bridge

(r - j / C) R 1

j C

R + 1j C

= Rj C

44

44

3

2

r = R CC

and C = C RR3

4

22

4

3

tan = C4R4

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The Transformer Ratio-arm Bridge

AC

A

B

C

D

N1

N2

I1

I2

detector

Z1

Z2

Figure 2.3: Transformer Ratio-Arm Bridge

ZZ

= NN

1

2

1

2

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5.0 HIGH VOLTAGE TESTING OF ELECTRICAL APPARATUS

Impulse testing on transformer

According to BS 171: Part 3. Carried out at room temperature with the transformer not energized.

Used standard impulse waveshapes. Full and chopped waves. During the tests, impulse voltage and current are recorded.

Failure detection (Insulation failure) A change in the waveshape of the voltage and current both before and

after the chopped waves have been applied. The existing of acoustic noise. Visual signs of flashoverFailure location : Voltage waveform propagation may provide clue to the

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Testing on switchgear or circuit breaker

According to BS 5227: Part 2, IEC 56. Conducted in two conditions:

Circuit breaker closed (ON position) Circuit breaker opened (OFF position)

15 negative and positive standard lightning impulse are applied. Test on one phase, the other two phases and structure of the panel is

connected to earth.

Routine and Type test on cables

According to BS 923: Part 2, IEC 60-2, IEC 55-1, IEC 230 and BS 6480. PD, Power frequency, conductor resistance, direct current and impulse

voltage tests.

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TRANSFORMER STANDARD TESTING PROCEDURE

Routine Tests Tests required for each individual transformer such as resistance measurements, voltage ratio and loss measurement.

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TRANSFORMER STANDARD TESTING PROCEDUREType- or design tests :

Conducted on a transformer which is representative of other transformers to demonstrate that these transformers comply with specified requirements not covered by routine tests, eg. temperature rise test and lightning impulse test.

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TRANSFORMER STANDARD TRANSFORMER STANDARD TESTING PROCEDURETESTING PROCEDURE

Special- or other tests : Tests other than type- or routine tests agreed to by the manufacturer and the purchaser, eg.measurement of zero-sequence impedance and sound level measurement.

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Lightning Impulse Test

LowLow--frequency tests alone are not frequency tests alone are not adequate to demonstrate the dielectric adequate to demonstrate the dielectric strength of transformers. strength of transformers.

The impulse voltage stress imposed on The impulse voltage stress imposed on windings by lightning phenomena can be windings by lightning phenomena can be very different from the low frequency very different from the low frequency voltage distribution. voltage distribution.

The lightning impulse test is performed The lightning impulse test is performed to prove the transformers ability to to prove the transformers ability to withstand transient voltages withstand transient voltages

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Lightning Impulse TestThe basic waveshapes have been defined The basic waveshapes have been defined

and the impulse voltage levels, referred to and the impulse voltage levels, referred to as the basic lightning impulse insulation as the basic lightning impulse insulation level (BIL), have been established for level (BIL), have been established for respective standardized voltage classes. respective standardized voltage classes.

By defining amplitudes and waveshapes, By defining amplitudes and waveshapes, however, a minimum impulse dielectric however, a minimum impulse dielectric strength is established which the strength is established which the transformer should meet.transformer should meet.

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Lightning Impulse Test-Test Waveshape

101

Lightning Impulse Test- Test Connection

The voltage is applied to each The voltage is applied to each line terminal in succession. line terminal in succession.

All other terminals shall All other terminals shall nominally be earthed directly or nominally be earthed directly or through lowthrough low--ohmic current ohmic current shunts. shunts.

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Lightning Impulse Test- Test Connection

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Lightning Impulse Test- Test Sequence

The test sequence consists of one reference impulse(RW) at 60% of full amplitude (FW):1RW 50 -70% amplitude 1 FW 100 amplitude1RCW 50-70% amplitude2 CW 100% amplitude2 FW 100% amplitude

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Lightning Impulse Test- Failure Indications

Detection of faults at impulse testing is based on comparison of voltage and current records obtained at reduced and full amplitudes

The two traces should have a perfect match to constitute evidence that the insulation has passed the test

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TESTING ACTIVITIES AT IVATTESTING ACTIVITIES AT IVAT

High voltage AC withstand test on 11 kV XLPE single core cable

(TOPLINK SDN BHD)

High voltage lightning impulse test on cast resin transformer

(LKH POWER TRANSFORMER SDN BHD)

High voltage lightning impulse test on 11 kV switchgear(MAHKOTA MANUFACTURING SDN BHD)

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TESTING ACTIVITIES AT IVATTESTING ACTIVITIES AT IVAT

Impulse Withstand Test on 630 kVA, 11/0.433 kV (top) and

20 MVA, 33/11.5 kV (bottom) Three Phase Power Transformer

(MALAYSIAN TRANSFORMER MANUFACTURING SDN BHD)

Cable jointing works for preparation of high voltage withstand test

(TOPLINK SDN BHD)

hv2

Documents

high voltage testing

high voltage generation

higher voltage

vmaxve halfcycle

high currents

high current ac

voltage doubler circuitsdr

halfwave ripple