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.
