Tandelta Basics

8/13/2019 Tandelta Basics

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Knowledge IsPowerSMApparatus Maintenance and Power Management

for Energy Delivery

Doble Engineer ing Com pany

Electrical Insulation Modeling


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Scope

Prevention of Apparatus Failure andPower System Interruptions due toInsulation Failure

Enhance System ReliabilityMinimize Damage to ApparatusEnhances Safety to PersonnelMinimize Loss of Revenue


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Benefit

Extension of Apparatus LifeDegradation of Insulation, if detected before failure, cangenerally be restored to its original conditionDefer replacement costs

Better Utilization of ResourcesInspection interval may be safety extended or scheduledto utilize resources efficiently and effectively

Variation of new apparatusVerify that new apparatus meets purchased specification and

agrees with factory test reportsAssures proper field Assembly


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Definition

What is a Power Factor/ DissipationFactor/Tangent Delta Test?

The underlying principle of this test is to measurethe fundamental AC electrical characteristics ofinsulation.


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Definition

InsulationIEEE Defines Insulation as:Material or acombination of suitable non-conductingmaterial that provides electrical isolation oftwo parts at different voltages.


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Clarification

Insulation vs. DielectricInsulation relates to a mediums ability to preventthe flow of current, I.e. poor conducDielectric implies that the medium or material has

specific measurable properties such as: DielectricStrength, Dielectric Constant, Dielectric Loss andPower Factor.


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In 1836, Michael Faraday (the father of the Capacitance

-- Just look at his name) discovered that when theplates between a capacitor were filled with anotherinsulating material, the capacitance would change.

This factor is the dielectric constant e

By definition the dielectric constant of a Vacuum is 1.0.All other dielectric constants are referenced to thisstandard.

Vacuum

Cvacuum=10 pF

Oil e=2.2

Coil= exVacuum = 22 pF

Dielectric Constant


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Dielectric Loss is the time rate at which electric

energy is transformed into heat in a dielectric when itis subjected to an electric field. The heat generated isgiven in terms of Watts.

iRWatts

Watts =E IR

Watts =Contamination + Deterioration

Contamination =Water + Carbon + Dirt

Deterioration =Carbon + Corona

Dielectric Loss


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Fundamental measurement

Fundamental AC ElectricalCharacteristics. . .

Total Current ITCapacitance CDielectric-Loss WDissipation Factor %DF or DFPower Factor %PF or PFResistance R


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PerfectInsulator

The Capacitor


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Ideal Insulation System

Evaluating Insulation System


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Current and Capacitance


Total Current ITCapacitance C

Dielectric-Loss WPower Factor %PFResistance R

} Evaluate physical makeup ofspecimen, size dependent


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Real Insulation Model

Simplified Equivalent Circuits of an Insulation Specimen

Series Circuit

RS

CS

CP

Parallel Circuit


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No phase shift

The Perfect Resistor

-1.5

-1

-0.5

0

0.5

1

1.5

0.

1

0.

7

1.

3

1.

9

2.

5

3.

1

3.

7

4.

3

4.

9

5.

5

6.

1

6.

7

7.

3

7.

9

8.

5

9.

1

9.

7

10.

3

10.

9

11.

5

12.

1

Time

Magnitude

Voltage

Current


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Resistive Component

The Resistor

IR

IR= IT

IR

= E/R

W=EIR

q= oE


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Real Component



Dielectric-Loss WResistance RPower Factor %PF

}Evaluate quality of thedielectric material, size

dependent


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Basic Insulation Circuit

Basic Power/Dissipation Factor Circuit


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Power Factor Is Size Independent

IC2 Specimen 1: 5 MVA TransformerSpecimen 2: 10MVA Transformer

remains the same regardless of the size of the transformer

Power Factor is an evaluation of the quality of the insulation

and is size independent

IT2

IR2 EIR1

IC1 IT1


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Definition

The Term Power/Dissipation Factor DescribesThe phase angle relationship between the applied voltage

across and the total current through a specimen.

The ratio of the real power to the apparent power.The relationship between the total and resistive current


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Basic Insulation & Power Factor Theory



Dielectric-Loss WResistance RPower Factor %PF} Overall evaluate of the

insulation (physical and

quality) requires at once one

other piece of information,

size independent


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Measurement Overview

V

Reference

Applied Voltage

Measure

Total Current Vector

Angle

Magnitude

Calculate

Capacitance

Power Factor

Real Loss (Watts)

IT

Watts

Capacitanc

e


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Basic Insulation & Power Factor Theory

Power Factor Vs. Dissipation Factor Vs. Tangent Delta

E

Q

d

IR

IC ITPower Factor = =

I

I

Dissipation Factor = =I

I

R

T

R

C

COS

TAN

Q

d

Q % PF (% COS Q) d % DF (% TAN )

90 0 0 089.71 .500 .29 .500

84.26 10.00 5.74 10.05

0 100.00 90 INFINITY


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Voltage sensitive characteristics

When we closely examine insulation, very small

gaps or voids could exist. These voids developan electrostatic potential on their surfaces. Thesesmall gaps become ionized: PartialDischarge/Corona.

Voids


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Power Factor vs. Test Potential

As test voltage is increased, the power factor will increase dependingon the void density.

Tip-Up = Power Factor at Line-to-ground voltage -Power Factor at 25% Line-to-ground voltage

Tip-up occurs in dry-type insulation specimens such as Dry TypeTransformer, rotating machinery, and cables.

25% L-G L-G

E

%PF

%PF @ 25% L-G

%PF @ L-G


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Knowledge IsPowerSMApparatus Maintenance and Power Management

for Energy Delivery

Doble Engineer ing Com pany

Measurement Principle


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Basic Laws of Electricity

A Difference in Potential Must ExistBetween Two Points in order forcurrent to flow

Current Always Returns to ItsSource

Current Always Takes the Path ofLeast Resistance


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Grounded-Specimen Test Mode (GST-


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Grounded Specimen Test Mode (GSTGround)

GuardTest Ground

High-Voltage Cable

Low-VoltageLead

Test-SetGround Lead

Test-SetStep-UpTransformer

Current &LossMeter

Grounded-Specimen Test Mode (GST-


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Grounded Specimen Test Mode (GSTGuard)

Current &LossMeter

Guard

Test Ground

High-Voltage Cable

Low-VoltageLead

Test-SetGround Lead

Test-Set

Step-UpTransformer

U d d S i T M d (UST)


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Ungrounded-Specimen Test Mode (UST)

Current &LossMeter

Guard

TestGround

High-VoltageCable

Low-VoltageLead

Test-SetGroundLead

Test-SetStep-Up

Transformer

M C d C


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Guard

High-VoltageCable


TestGround

Low-

VoltageLead Test-Set

GroundLead

Current &LossMeter

CA CB

IA IB

IA+IB

GST-Ground

Measure CAand CB

M C G d C


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Guard

High-Voltage

Cable


TestGround

Low-

VoltageLead

Test-Set

GroundLead

Current &LossMeter

GST-Guard

CA CB

IA IB

IB

Measure CAGuard CB

M C G d/G d C


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Guard

High-Voltage

Cable

Test-Set

Step-UpTransformer

TestGround

Low-VoltageLead

Test-SetGroundLead

Current &LossMeter

UST

CA CB

IA IB

IA

Measure CAGround/Guard CB

M C + C + C


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Guard

High-VoltageCable


TestGround

Low-VoltageLeads

Test-SetGroundLead

Current &LossMeter

CB

CC

IB

IC

IA+IB +IC

GST GroundRed + Blue

Measure CA+ CB + CC

CA

IA

Meas e C + C


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Guard

High-VoltageCable


TestGround

Low-VoltageLeads

Test-SetGroundLead

Current &LossMeter

CB

CC

IB

IC

IB +IC

GST Gnd RedGuard Blue

Measure CB + CC

CA

IA

Measure C + C


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Guard

High-VoltageCable


TestGround

Low-VoltageLeads

Test-SetGroundLead

Current &LossMeter

CB

CC

IB

IC

IA+IC

GST Gnd BlueGuard Red

Measure CA+ CC

CA

IA


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Measure C + C


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Guard

High-Voltage

Cable


TestGround

Low-VoltageLeads

Test-SetGroundLead

Current &LossMeter

CB

CC

IB

IC

IA+IB

UST MeasureRed + Blue

Measure CA+ CB

CA

IA


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Measure C


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Guard

High-Voltage

Cable


TestGround

Low-VoltageLeads

Test-SetGroundLead

Current &LossMeter

CB

CC

IB

IC

IA

UST MeasureBlue Gnd Red

Measure CA

CA

IA

Test set shielding


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Test set shielding

Understanding Electrostatic Interference

StaticSource

Specimen

Current &

Loss Meter

It

Ie+ Ie

Ie+ Ie

Ie

Ie

Ie

Ie

IT

Ie

IeTest

SetGroundShield

TestSetGuardShield

Ie Ie Ie Ie

Ie

LV Lead

Guard

Shield

Ground

Shield

Test Cable

Terminations

High-Voltage Test Cable

Test Cable Guard Shield

Test Cable Ground Shield

Electrostatic Interference


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Electrostatic Interference

Characteristics of Interference

IR

IC

IL

Electrostatic Interference and


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Measurements

IR

IL

W W

IT

IT

Traditional suppression method


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Traditional suppression method

Interference Suppression - Line Sync Reversal(Traditional)

Reports the average of the normal and 180 degreereversed reading at 60 Hz. It is only effective when thespecimen current is greater than the interference current.

The test frequency is obtained from the 120/240-volt linefrequency. Some difficulties may be encountered whenusing an unstable frequency source with this type of test.

IR

IC

IR

IC

Updated approach to interference


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p ppcancellation

Interference Suppression - Line FrequencyModulation Reports the computed result at line frequency of the two

measurements at +-5% of the line frequency, e.g. 57 and 63 Hz.This method minimizes the effects of electrostatic interference andyields superior results in high levels of electrostatic interference.

The test frequency is obtained from an internal oscillator. This type

of test creates a synthesized test voltage that is isolated from theinput and offers better performance using a generator or DC to ACinverter

Measurements

Current

6357 60 Frequency (HZ)

Interference

Input voltage interference


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Input voltage interference

Causes

Portable power supply

Power quality issue

Cannot be suppressed

Stability will affect accuracy of measure

Test signal should be independentto power line frequency

Issue to consider when testing


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Safety!

Isolate and ground apparatus under test Work between visible grounds

Ground M4100

Connect test lead to the M4100 first

Never come in contact with the test leadswhile testing

Isolating test specimen

Issue to consider when testing

Date post:	04-Jun-2018
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Tandelta Basics

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