Page 524 - IRSEM_Main Book

(c) QBAT: It's pick up voltage is 1.75 V and pick up current is 175 ma approximately. This
is achieved by the provision of a biasing permanent magnet on its core along with its
copper slug. It has only one core and 2F-2B contacts. This can be used Upto 750
meters track Circuit Lengths with choke in RE Areas. This is made to RDSO
specification. No. 84/88. Usage: it is used as track relay in RE area.

5.0 Timer Relays

(a) Types & Usage of Timer Relays: These relays are used in the signaling circuits to
release interlocking after certain period of time to ensure safety. Following types of
Time Element Relays are in use (i) DC Thermal type (ii) Siemens Motorised Clock Work
time relay (iii) Motor type (iv) Electronic type.

(b) DC Thermal Type Element Relay (QJ1): This type of relay employs heat operated
contact associated with an ordinary DC Neutral Relay. It has a heating element (H)
and a neutral line relay (R) which together energise an external line relay after a pre-
set time delay. One of such type is “QJI” type relay. Features of this relay are: (i)
Rated Voltage 24 V DC or 50 V DC (ii) Heat coil resistance 40 to 42 Ohms (iii) Max.
Heating power 15 Watt at rated supply Voltage. The Maximum numbers of
operations should be restricted to 100/day otherwise characteristics of the heating
element may change. An increase of 10% in applied voltage may result in a time
decrease of up to 10%. An decrease of 10% in applied voltage may result in a time
decrease of up to 20%. Usage: these relays are used to count time delay in Signalling
Circuits.

(c) Electronic Timer Relays: Fail safe Electronic Timer Relays are being used to achieve
time delay either by charge, discharge method or counting by clock pulse or
integrated circuits. Usage: These relays are used to count time delay.
6.0 Metal to Metal Relays

(a) K-50 Relays: K-50 relays are available only in group units of different sizes.
Depending upon the unit size, these groups are broadly classified as: (i) Mini group (ii)
Minor Group (iii) Major group. The capacities of various groups are as follows (i) Mini
Group: 2 Neutral control relays, 2 Interlocked relay or ECR with power conversion
unit. (ii) Minor Group: 15 Neutral (with one interlocked relay replacing two neutral
relays, one contactor relay replacing four neutral relays, or one resistor or condenser
fixed in place of one neutral relay in some units. (iii) Major Group (used only in RRI):
Up to 30 relays space with combination of Neutral and interlocked relays, One
contactor relay replacing four neutral relays space one resistor and condenser fixed in
placed of one neutral relay in same group.

(b) Group relays in Siemens interlocking: (a) 2-Aspect Signal Group (b) 3-Aspect Signal
Group (c) Shunt Signal Group (d) Universal Route Group in PI, RRI (e) Point Group for
PI (f) Point Group for RRI (g) Point Chain Group for RRI.

(c) Non AC immunised Neutral Relays: These relays are available in 4F/4B, 5F/3B &
6F/2B contact configurations. The ohmic values of these relays are 1260 ohms for
4F/4B, 1260 ohms for 5F/3B and 1840 ohms for 6F/2B.

Chapter 21: Relay & Electronic Interlocking Page 467 of 535