This document discusses feeder and bus bar protection and covers plug setting multipliers (PSM) and time setting multipliers (TMS) used in electromechanical relays. PSM indicates the severity of a fault by setting the ratio of actual fault current to relay pickup current. TMS sets the relay tripping time by adjusting the distance between a rotating disk contact and relay coil. An example shows how PSM and TMS are used to calculate relay operating time for a given fault current.

1. LENDI INSTITUTE OF ENGINEERING AND TECHNOLOGY
Jonnada, Andhra Pradesh- 535005
Department of Electrical and Electronics Engineering
UNIT -IV
FEEDER AND BUS BAR PROTECTION
Presented by,
Dr. Rohit Babu, Associate Professor

2. Syllabus
Department of Electrical and Electronics Engineering
∟Protection of lines
―Over current Protection schemes
―PSM, TMS
―Numerical examples
―Carrier current and three zone distance relay using impedance
relays
―Protection of bus bars by using Differential protection

3. PSM & TMS
Department of Electrical and Electronics Engineering
• Plug Setting Multiplier (PSM) and Time Setting Multiplier (TMS) are
used only for Electromechanical Relays.
• PSM and TMS settings are the settings of a relay used to specify its
tripping limits.
• Plug setting multiplier (PSM) Indicates the severity of the fault.

4. PSM & TMS
Department of Electrical and Electronics Engineering
• Plug Setting Multiplier actually refers how dangerous the fault is and in
what time it should be cleared. Changing the position of plug changes
the number of turns of the pickup coil.
• Time Multiplier Setting used to change the value of operation of the
relay. If it is more the relay will take more time to operate and vice versa.
Changing the position of TMS setting, changes the distance between the
contact of the rotating disk and the coil.

5. PSM & TMS
Department of Electrical and Electronics Engineering

6. PSM & TMS
Department of Electrical and Electronics Engineering
PSM is nothing but a ratio between the actual fault current in the relay operating coil
to pick up current (the relay current setting).
Fault Current
PSM=
Relay Pick up Current
Relay pick up current % current setting CT ratio
 
Fault Current
PSM=
% current setting CT ratio

In other words, the ratio between the CT secondary current to relay operating current is
called PSM.

7. PSM & TMS
Department of Electrical and Electronics Engineering
CT Secondary Current
PSM=
Current Setting in the Relay
The plus setting multiplier is used only in electromagnetic relays, not in
numerical relays. Therefore, the numerical relay does not require plugs.

8. Example
Department of Electrical and Electronics Engineering
1. If the plug position 5 means the relay operates when the fault current is 5 times of
the CT ratio. i.e The supply CT is rated 400:5A and the fault current will be 3200A
means, the plug position is 5 then the relay operates, because of the relay gets the
current value of 25 Amps.
Sol.
3200
8
5
PSM  
• The operating Times is depending upon the PSM. The high value of PSM indicates low operating
time. In our case PSM is 8, hence the relay trip the circuit in 2 seconds wheres the TMS is 100%.

9. PSM & TMS
Department of Electrical and Electronics Engineering
Time Setting Multiplier (TSM):

10. PSM & TMS
Department of Electrical and Electronics Engineering
What is TMS or Time setting multiplier:
• TMS is nothing but an adjusting or speeds up the tripping mechanism of the relay (it is
called as the dial).
• The dial is nothing but a rotating disc, which rotates when the fault current in the relay
coil reaches the pickup current.
• It means, one end connects with the tripping mechanism and another end connect with
the relay operation mechanism.
• By changing the dial or disc position we can increase or decrease the tripping time of the
relay.

11. PSM & TMS
Department of Electrical and Electronics Engineering
• Here the position zero indicate
the tripping position and green
colour shade indicate the
operating position. In the first
disc, position indicates the TMS
is 10%.
• It means the relay operating
time is 10% of the Plug setting
multiplier time. Time setting
value will be 10%, 25 %, 30 %
…100% like that.

12. PSM & TMS
Department of Electrical and Electronics Engineering
The total relay operating time= Plug setting Multiplier time (Which is available in the
relay) * Time Multiplier Setting
Take an example of the above mentioned, in this, consider relay TMS is 10% and PSM=8..
Hence the timing for PSM 8, Time =2 sec…then the relay operating time is 2 * 10% = 0.02sec.