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Tuesday, 23 July 2013

Relay code of pratice


Relay code of practice
Relay code of practice

1.        The entire wiring of circuitry for indications, alarms, metering and protection should be permanent wiring.
2.        The leads should be marked and identified by ferrules near terminals.
3.        Every lead should end at a terminal point and no junction by twisting is allowed.
4.        The wiring should be by copper leads for C.T secondary for all cores i.e. metering cores as well as protection cores and for PT secondary for protection core.
5.        The wiring should be by copper leads 1.07 The copper lead for 1.05 & 1.06 above should be stranded but not single lead type.
6.        Aluminium leads can be used for indication, alarms and PT secondary for metering but stranded wires only are to be used. But copper leads are always preferable for these said purposes.
7.        The terminations should be lugged by ring shape ‘O’ lugs. ‘U’ shape lugs should be avoided since ‘U’ shape lugs may slip if terminal is loosen.
8.        For CT Secondary terminations, two nuts with one spring washer and two flat washers to be compulsorily used.
9.        The CT terminal strips should be stud type with nuts and not screw-in-type.
10.    Wherever two sets of batteries are available, the primary protection and back-up protection should be from different batteries.
11.    Where there is only one battery at an Electrical Power Substation, the primary and back-up protections should be given D.C supply through two individual circuits with independent fuses run from D.C bus.
12.    When CBs have two trip coils, both main protection and backup protection will energize both the trip coils.
13.    D.C and A.C supplies should not be taken through different cores of the same cable. Totally different cables should be used for DC and AC supplies.
14.    Independent D.C cables should be run to each equipment in the yard and looping of D.C supply from one equipment to other is not permitted.
15.    The D.C emergency lighting in substation should be through independent cables and not mixed up with protection and other circuitry.
16.   Standard colour codes for wires in control circuit of different sizes should be as follows,

sr.
PURPOSE
SIZE
COLOR
1
Indication, Alarm, trip, close etc
1.5 mm2
 Gray
2
 Red Phase Metering PT Circuit
1.5 mm2
Red
3
 Yellow Phase Metering PT Circuit
1.5 mm2
Yellow
4
 Blue Phase Metering PT Circuit
1.5 mm2
Blue
5
 Red Phase Protection PT Circuit
2.5 mm2
Red
6
 Yellow Phase Protection PT Circuit
2.5 mm2
Yellow
7
 Blue Phase Protection PT Circuit
2.5 mm2
Blue
8
 Red Phase Metering and Protection CT Circuit
2.5 mm2
Red
9
 Yellow Phase Metering and Protection CT Circuit
2.5 mm2
Yellow
10
 Blue Phase Metering and Protection CT Circuit
2.5 mm2
Blue
11
Phase for auxiliary AC supply
2.5 mm2
Red
12
Neutral for auxiliary AC supply
2.5 mm2
Black
13
Common star point of CTs
2.5 mm2
Black
14
Common star point of Protection PTs
2.5 mm2
Black
15
Common star point of Metering PTs
1.5 mm2
Black
16
Earthing Connection
2.5 mm2
Green

17.   The lead numbers are also standardized as follows so that anyone can easily identify the purpose for which the lead is connected-

sr
Alphabet Series
Purpose
Example
1
 J Series
 D.C Incoming
 J1, J2, etc.
2
 K Series
 Control – Closing, Tripping, etc.
K1, K2, K3 etc.
3
 L Series
 Alarms, indications and annunciations
 L1, L2, L3, etc.
4
 M Series
 Motor Circuit
 M1, M2, etc.
5
 E Series
 Potential transformer secondary
 E1, E2, E3, etc.
6
 H Series
 LT A.C Supply
 H1, H2, H3, etc..
7
 A Series
 C.T secondary for special protection
 A1, A2, A3, etc.
8
 B Series
 Bus bar protection
 B1, B2, B3, etc..
9
 C Series
 Protection Circuits
 C1, C2, C3, etc.
10
 D Series
 Metering Circuit
 D1, D2, D3, etc

18.   The CT ratios available and adopted with number of cores shall be displayed on each panel as follows: (with underlined position as adopted).
19.   400 – 200 – 100 / 1-1-1
20.   19 Wherever CT cores are not used “SHORTING LOOPS” should be provided in CT secondary terminals and not in marshalling boxes or at panels.
21.   20 The Cable entries in the equipment, marshalling boxes and panels should be through appropriate size of cable glands. No other means are allowed.
22.   21 PT secondary should have group MOCBs with D.C alarm.
23.   22 Few cells from a battery set should not be used for separate low voltage D.C circuits. Here D.C – D.C converters may be employed for utilizing full D.C voltage of the entire battery as input.
Standard lead numbers used in control circuit of protection of power system
Certain lead numbers are standardized as follows and should be compulsorily adopted with ferrules at terminations of leads.
Main DC Positive supply – J1
 Main DC Negative supply – J2
 DC Positive bus inside panel – K1
 DC Negative bus inside panel – K2
Remote Close - K15R
 Remote Trip - K5R
 Local Close - K15L
 Local Trip - K5L

 Metering CT secondary’s – D11, D31, D51, D71 etc.
 Protection CT secondary – C11, C31, C51, C71 etc.
 Special Protection CT secondary – A11, A31, A51, A71 etc.
 PT secondary – E11, E31, E51, E71 etc.

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