Lecturer Note - HV Network

7/27/2019 Lecturer Note - HV Network

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HV DISTRIBUTIONSYSTEMS


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Types of HV Network

Single -end radial fed

Ring network

Interconnected mesh


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Single radial

Single -end radial fed

Customer substations are connected to theprimary substation.

Low supply security because of single pointof failure.

Long supply restoration time in case of fault


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Typical 11kV radialarrangement

V

VV

VVV

V

VV

V

VV

V

VV

VVV

V

VV

V

VV

V

VV

VV

V

V

VV

V

VV

V

VV

VV

V

V

VV

V

VV

VVV

Switch/Isolator

Transformer


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Ring network

Double-end fed with an NO point

To provide a higher supply security, thecustomer substations can be fed from 2

sources. Ringed network with close point

Highest possible supply reliability


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Typical 11kV RMU open ringarrangement

Legend

Ring Main Unit

11 kV/LVTransformer

Normally Open

TransformerRoom

11kV Main

Substation


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Typical 11kV close ring

arrangement Each customer substation has dual supplyand a single circuit fault would not case anysupply interruption.

Feature: Each feeder is protected by either high-

speed feeder protection or pilot wire

protection with back up overcurrent andeath fault (OCEF) protection equipped in theprimary substation.


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11kV close ring arrangement

Transformer

Room

VVV

VVV

VVV

VVV

VVV

VVV

VVV

VVV

VVV

VVV

11kV Main

Substation

VVV

Circuit breaker

Transformer


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Interconnected mash

The 11kV interconnecting cables, normalopen at one end, is commonly adopted toconnect up 2 primary substations.

This arrangement,Utilize the spare capacity of the primary

substations more effectively

Provide mutual backup between 2 primarysubstations.


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Typical interconnectednetwork


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3-Class approach on supplysecurity classification

Power transmission from HV (500kV, 400kVor 132kV) to LV (11kV or 380kV) in thenetwork configuration causes the impact of

fault becoming smaller in terms of load lossmagnitude or no. of affected customers.

A different supply security arrangements are

adopted to different load group to preventwidespread load loss.


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Class 1 security

Criteria: loading group size below 1.5MVAor less than 500 customers

Single radial network is applied.


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Class 2 security

Criteria: load group of about 3.5MVA.

Open ring network with a mutual backup of2 supply networks


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Class 3 security

Criteria: load group up to 21MVA

Highest security with daul supply close ringnetwork


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Design Standard

What is N-1?

N-1 is security standard.


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Example: 132kV network

Loss of any single line for transmissioncomponent (Circuit or transformer)

No interruption


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Open ring circuit - Security

Open circuit with N-1


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11KV Schematic Diagram -1


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11KV Schematic Diagram -2


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Primary network

Lecturer Note - HV Network

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