Different Relay Device Number used in Protection of Power System
01 - The entire wiring of circuitry for indications, alarms, metering and protection should be permanent wiring.
02 - The leads should be marked and identified by ferrules near terminals.
03 - Every lead should end at a terminal point and no junction by twisting is allowed.
04 - 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.
05 - 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.
06 - Aluminum 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.
07 - 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.
08 - For CT Secondary terminations, two nuts with one spring washer and two flat washers to be compulsorily used.
09 - The CT terminal strips should be stud type with nuts and not screw-in-type.
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 color codes for wires in control circuit of different sizes should be as follows,
|Indication, Alarm, trip, close etc||1.5 mm2||Gray|
|Red Phase Metering PT Circuit||1.5 mm2||Red|
|Yellow Phase Metering PT Circuit||1.5 mm2||Yellow|
|Blue Phase Metering PT Circuit||1.5 mm2||Blue|
|Red Phase Protection PT Circuit||2.5 mm2||Red|
|Yellow Phase Protection PT Circuit||2.5 mm2||Yellow|
|Blue Phase Protection PT Circuit||2.5 mm2||Blue|
|Red Phase Metering and Protection CT Circuit||2.5 mm2||Red|
|Yellow Phase Metering and Protection CT Circuit||2.5 mm2||Yellow|
|Blue Phase Metering and Protection CT Circuit||2.5 mm2||Blue|
|Phase for auxiliary AC supply||2.5 mm2||Red|
|Neutral for auxiliary AC supply||2.5 mm2||Black|
|Common star point of CTs||2.5 mm2||Black|
|Common star point of Protection PTs||2.5 mm2||Black|
|Common star point of Metering PTs||1.5 mm2||Black|
|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.
|J Series||D.C Incoming||J1, J2, etc.|
|K Series||Control - Closing, Tripping, etc.||K1, K2, K3 etc.|
|L Series||Alarms, indications and annunciations||L1, L2, L3, etc.|
|M Series||Motor Circuit||M1, M2, etc.|
|E Series||Potential transformer secondaries||E1, E2, E3, etc.|
|H Series||LT A.C Supply||H1, H2, H3, etc..|
|A Series||C.T secondary for special protection||A1, A2, A3, etc.|
|B Series||Bus bar protection||B1, B2, B3, etc..|
|C Series||Protection Circuits||C1, C2, C3, etc.|
|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).
400 - 200 - 100 / 1-1-1
19 - Wherever CT cores are not used “SHORTING LOOPS” should be provided in CT secondary terminals and not in marshaling boxes or at panels.
20 - The Cable entries in the equipment, marshaling boxes and panels should be through appropriate size of cable glands. No other means are allowed.
21 - PT secondaries should have group MOCBs with D.C alarm.
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 Nagetive bus inside panel – K2
Remote Close - K15R
Remote Trip - K5R
Local Close - K15L
Local Trip - K5L
Metering CT secondaries – D11, D31, D51, D71 etc.
Protection CT secondaries – C11, C31, C51, C71 etc.
Special Protection CT secondaries – A11, A31, A51, A71 etc.
PT scondaries - E11, E31, E51, E71 etc.