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Diagnostic Insulation Testing Predictive Maintenance issues Basis of Insulation Tests Spot Tests & Polarisation Index Dielectric Discharge Test Power factor testing AVO Range

Maintenance Regimes Corrective maintenance Preventive (Periodic) Maintenance Predictive Maintenance (Record & trend data to determine next action - variable maintenance periods) Appropriate regime varies

Maintenance Regimes Value of Assets ? Critical role of Assets ? Costs of failure ? Costs of Maintenance regime ? Manpower Skills ‘Tools’ - Testing / Monitoring / I.T.

Why test insulation? System performance System safety System reliability Economic asset management Over 60% failures caused by Insulation problems (CEGB & ERA Technology)

Insulation Failure Oil Contamination Mechanical damage Pin holes Vibration Temperature cycling Moisture & humidity Cracks

Test Techniques - DC Testing Total Current has 3 components Capacitive Current - Charging Absorbtion Current -Polarisation Leakage Current TIME DEPENDENT Temperature Dependent

Insulation Test Currents 100 I/uA Charging Total 10 Leakage Absorption 1 0,1 1 10 T

Insulation Equivalent Circuit Leakage Capacitance Absorption

Diagnosis from Insulation Tests Record & Trend Spot Tests - Record conditions as well (Temp, RH) Time resistance tests - Polarisation Index Test (PI) Step Voltage Test (SV) Dielectric Discharge Tests (DD)

Insulation Test as a Go/NoGo Test Spot Test carried out for given time (1 minute) Commissioning National /Manufacturer’s Standards

Time Resistance Tests Independent of equipment size and temperature Some information without past results Options; Curves Time - Resistance Ratios

Time ResistanceTest Absorbtion current visible Absorbtion current not seen t1 t2 Time

Time Resistance Tests Polarisation Index Insulation Condition (10 min/1 min ratio) <1 1,0 - 2,0 2,0 - 4,0 >4,0 Insulation Condition unsatisfactory dubious good very good

Time Resistance Tests Dielectric Absorption Ratio (60 s/30 s) <1 1.0 - 1.4 1.4 - 1.6 >1.6 Insulation Condition unsatisfactory dubious good very good

Step Voltage Test Test voltage is increased in 5 steps Lower insulation resistance values at higher voltage indicate presence of cracks/holes

Step Voltage Test 5000 V Resistance 2000 V 1000 V Voltage

Dielectric Discharge Test Test is run until currents stabilise Measurements made on discharge DD = Current after 1 min Voltage x Capacitance

Dielectric Discharge Test + - - - - - - + - + + - + - + - + + - - + - + + - - + - + + + + + + - - + -

Dielectric Discharge Test DD Value >4 2.0 - 4.0 <2.0 Insulation Condition unsatisfactory dubious good

Tan Delta Testing Polarisation and capacitive current dominate Aging (moisture/dirt) sensitive Low voltages can be used

Perfect Insulation I (capacitive) ITOTAL IR = 0 V (applied)

Facts about Insulation In a “REAL insulation system” there is also a loss current flowing in-phase with the voltage // = IC IR ITOTAL

REAL Insulation I (capacitive) IC ITOTAL IR V (applied)

Facts about Insulation In practice NO insulation is perfect Resistive loss current is always present Total current leads the voltage by a phase angle  and lags capacitive current by angle 

REAL Insulation I (capacitive) IC ITOTAL d  IR V (applied)

What is Tan Delta? Tan Delta is the ratio of in-phase (resistive) current to the 90-degree (capacitive) current Tan Delta equals Dissipation Factor

What is Power Factor? Power factor is the ratio in-phase (resistive) current to the total current.

Tan Delta Testing I(capacitive) IR Tan d = IC IC ITOTAL IR Power Factor = d ITOTAL  IR V(applied)

Tan Delta v. Power Factor Both values are similar up to 20% power factor and tan delta; beyond 20% they diverge.

Tan Delta 3 Terminal Test Low voltage (L) High voltage (H) CHL CLG CHG Ground Connection (G)

Tan Delta 3 Terminal Test Configuration Measures GST L-GND CHL + CHG GST L-Guard CHG UST CHL GST H-Guard CLG GST H-GND CHL + CLG

Why perform the Tan Delta Test? Normal insulation resistance testing limited to 5kV dc Tan Delta is up to 12kV ac Most test specimens normally operate with AC voltage Much closer resemblance to the normal operating condition of the insulation

Tan Delta Testing Comparison with name -plate values Very sensitive to small changes a.c. test at rated voltage Larger, heavier test equipment

Insulation Test Diagnosis

Tests Performed On Transformers Circuit Breakers Rotating Machinery Insulating Liquids High Voltage Bushings Surge Arrestors High Voltage Coils

Diagnostic Testing - Where Used P.I. Testing & Trending Generators / Aerospace Petrochemical/Process Industry Transmission/Distribution Pass/Fail All electrical Equipment > 3 kV Commissioning & Routine Maintenance TREND to TRENDING !

MEGGER BM11D Portable, IP54 , large PbAcid battery Readings to 500 GOhm Display is large, clear & Easy to Use Safety features Automatic discharge, locking test leads, Hazard display Integral Timer

MEGGER BM21 All BM11D features plus; Readings up to 5TOhm Selectable Test Voltage Selectable Test Time Checks Capacitance at test End Can show current as well as resistance Burn mode

MEGGER BM25 As BM21 features plus; Automated tests Polarisation Index Step Voltage Dielectric Discharge RS232 download results every 5 s Download software & lead

MEGGER S1-5005 As BM25 with 5 mA test current. BM25 has 2 mA test current.

MEGGER S1-5010 Heavy Duty - Mains & Battery Automated Tests Results Storage RS 232 communications Graphical Display

MEGGER S1-5010

MEGGER S1-5010 Memory for 75 sets of results Windows PC software remote operation results storage External output for HV “ON” indicator Switchable digital filter for noise rejection IP54 weatherproofing

S1-5010 and S1-S1 software S1-5010

S1-S1 software Duplicates the S1-5010 on your PC screen. Control the S1-5010 from your PC via an RS232 link. Download tests to your PC in real time. as a batch at the end of testing. Annotate the tests results with details of the test. Recreate graphs etc. in other software.

Test Start/Stop button Instrument On/Off switch S1-5010 via software Voltage ON lamp S1-5010 Soft keys Soft keys Test Start/Stop button Instrument On/Off switch Soft keys

S1-S1 Menu Bar - Window Remote Control Database Viewer Selects the remote control window if a Database Viewer window is active. Database Viewer Selects a database viewer window if the Remote Control window is active or switches between Database Viewer windows if more than one is active.

Database Viewer - Details

Database Viewer - Graph

MEGGER EDA Electronic Dielectric Analyser Used on rotating machines Simple to use Automatic testing Normalised parameters Database of results

MEGGER EDA

MEGGER EDA Insulation of rotating machines Technique used for 15 years hydraulic power generators turbo-generator 6/12 kV motors Technique used for 15 years

EDA Software Notes:

MEGGER EDA Automatic testing PC controlled Motor data input Test voltage input Calculation of results

EDA Software Notes:

MEGGER EDA Results at 2 test voltages Resistance Polarisation Index Time constant (RC) Dielectric Discharge Absorption Index Capacitance (ac & dc)

EDA Software Notes:

MEGGER EDA Results Print out report Print out graphs Expert analysis Comparison with previous results

BIDDLE Delta 2000 500 V - 12 kV power factor tester Automatic bridge operation High noise immunity Menu driven display Measures voltage, current, power (loss), power factor/tan-delta and capacitance

BIDDLE Delta 2000 Results storage Printer for on-site results Downloading test data Accessories Oil test cell Bushing connectors Bar code wand

BIDDLE Delta 2000

BIDDLE 2.5 & 12 kV semi-automatic units 2.5 kV single unit construction 12 kV control unit and Measure capacitance, dissipation factor and Watts

CB-100 Low Voltage Bridge 28 V test voltage Safe Compact Low cost Often used on bushings & transformers

Testing with Safety How does the electrical risk appears ? - When an electrical line or conductor is unexpectedly still live - When current sources are not properly isolated - When power generators are connected to the network - When there are atmospheric phenomenons such as lightning - Through induced currents

Testing with Safety However, it has also been observed that the most common causes of unexpected presence of voltage on electrical lines or installations were due to: - A mistake in operating a switch - A mistake in identifying the work to perform - A "faulty" switch (one of the links for example remaining partially engaged)

Testing with Safety How does the electrical risk disappear ? 1. By observing Simple Electrical Safety Rules directed by common Sense (even if Working Practices vary from a country to another, GOLDEN RULES always apply). 2. By using Simple, Light and Reliable Electrical Safety Equipment.

Testing with Safety 1. SEPARATE THE WORK AREA FROM ALL POSSIBLE SOURCES OF POWER SUPPLY by opening circuit-breakers, switches… AND LOCK THE LINKS IN THE OPEN POSITION

Testing with Safety 2. CHECK THE ABSENCE OF VOLTAGE at source and on site, on each conductor and apparatus involved. 3. APPLY APPROPRIATE SHORT- CIRCUIT AND EARTHING SYSTEMS in sufficient numbers on the conductors of your network where operation is taking place.

Testing with Safety 4. SHOWN, WARN OTHERS AND LIMIT THE WORK AREA even during the most simple temporary maintenance operation

Testing with Safety Discharge Sticks Slowly discharge capacitive items (cables, capacitors….) Discharge to a safe level in 5 - 10 times RC (time constant)

Discharge Sticks Voltage Length Resistance Max. cap. 35 kV 50 cm 10 kOhm 6 uF 50 kV 136 cm 100 kOhm 6 uF 75 kV 156 cm 150 kOhm 4 uF 100 kV 176 cm 200 kOhm 3 uF 150 kV 208 cm 300 kOhm 2 uF

MEGGER Foster Oil Electric Strength Testers Oil Testing MEGGER Foster Oil Electric Strength Testers

Why test switchgear oil? Prevent Transformer failure Principle problems are: humidity oxygen temperature

Oil Testing Methods Water content Acidity Colour Flash point Gas content Oil provides HV insulation Electric strength is the most important test

Electric strength Test techniques Electrode gap Electrode shape Vessel size Voltage rise rates Stand and stir times

Electric strength test results Temperature affects values Record results Low results show presence of moisture or particles Impurities from air, operator or equipment

Breakdown Testing

Electric Strength Test Results Average over six tests Scatter can be large Standard deviation calculated Report breakdown values, date, temperature

New Specification EN60156 Replaces IEC156 (1963) Optional stirring Current limited breakdown for silicone oils Gives guidance on scatter of results

Withstand Testing Test voltage held at preset level for 1 minute Quick test of level of contamination Increase to breakdown to find headroom?

Withstand Testing

MEGGER Foster OTSAF/2 Fully automatic, unattended operation Wide range of tests including five custom Results include standard deviation, time, date Results printed or download via RS232 Stirring options for magnetic or propellor 60 kV, 80 kV and 100 kV versions

MEGGER Foster OTSAF/2

MEGGER Foster OTS60PB Portable oil test set for on site measurement Battery powered for two days continuous use Fully automatic, unattended operation Pass/fail levels for go/no go testing Small and lightweight (19 kg = 42 lb) Complete with battery charger Variety of electrodes RS232 interface plus optional printer

MEGGER Foster OTS60SX Low cost, Semi automatic set 60 kV maximum output, 0,1 kV resolution Simple START, STOP & PAUSE control Weighs only 17,5 kg Optional vessels for all specifications Auto 60 second timer for withstand testing Operates from 110/230 V power supply

MEGGER KF2000 Karl Fischer moisture in oil test set Simple to use Quick results Low cost Battery powered, portable

MEGGER KF2000

Bringing Reliability to Amps Volts Ohms AVO INTERNATIONAL Bringing Reliability to Amps Volts Ohms 15 15

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