1. ME PRESENTATION
ON
INSULATION COORDINATION
PREPARED BY :
UPADHYAY RAKSHITA R.
Er No : 140370707018
Roll No : 24

2. Contents….
 Introduction
 BIL
 Insulation Coordination Process
 Conclusion
 References
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3. Introduction :
 Purpose: To determine the necessary and sufficient
insulation characteristics of the various network
components in order to obtain uniform withstand to
normal voltages and over voltages of various origins .
 Objective: Ensure safe, optimised distribution of
electrical power.
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4.  Insulation Coordination (IEEE)
 The selection of insulation strength consistent with
expected over voltages to obtain an acceptable risk of
failure.
 The procedure for insulation coordination consists of
(a) determination of the voltage stresses and
(b) selection of the insulation strength to achieve the
desired probability of failure.
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5. Basic insulation level :
 BIL : To establish definite common level for all the
insulation in the station and bring all insulation to or
above this level.
 Fundamental requirements,
a) The selection of a suitable insulation level,
b) The assurance that the breakdown or flashover strength
of all insulation in the station will equal or exceed the
selected level,
c) The application of protective devices.
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6. Insulation coordination process:
 Considerations:
 Understanding Insulation Stresses
 Understanding Insulation Strength
 Designing Methods for Controlling Stresses
 Designing Insulation Systems
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7. Process:
a) Specify the equipment insulation strength, the BIL and
BSL of all equipment.
b) Specify the phase‐ground and phase‐phase clearances
that should be considered.
c) Specify the need for, location, rating, and number of
surge arresters.
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8.  Transformers, Isolators, Instrument Transformers are
manufactured for the standard Insulation level.
 Where LAs are provided right on the top of the
transformer, some of the equipment may lie well out side
the protective zone of the LA.
 Protective zone is determined based on
a) With stand level of equipment
b) Discharge volt of LA
c) Distance between LA and equipment.
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9.  Such equipment shall be designed for one step higher
Bill.
 Generally BIL of substation equipment other than
transformer are designed for10% higher BIL than that of
Transformer.
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10. Conclusion :
 Insulation coordination aims at finding the right balance
between equipment reliability from a dielectric
standpoint, on the one hand, and their sizing and thus
cost, on the other.
 A key component of insulation coordination is pairing the
correct strength to the correct stress.
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11. References :
 Insulation coordination studies “the selection of
insulation strength” ,adam sparacino, mitsubishi electric
power products, inc.
 Insulation coordination by a. c. monteith and h. r.
vaughan, revised by : a. a. johnson.
 Electrical transients in powersystems by Allan
greenwood willey publication second edition (indian
edition)
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