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.