1. Electrical Distribution Training
Training for Sepam Series 20/40/80
Control and monitoring functions

2. Load shedding principle
Motor load shedding is done to reduce the load on the electrical system so as to keep the voltage within an acceptable range.
Block diagram

3. Load shedding implementation
Setting the load shedding function
The outputs for load shedding orders and inhibition of closing are part of the switchgear control function.

4. Restart principle
With this function, motors can be automatically restarted after a shutdown triggered by a voltage dip (load shedding).
The restart function is to be associated with the load shedding function. It allows staggered restarting of process motors as long as the voltage dip that caused load shedding was brief.

5. Restart implementation
Setting the restart function
The outputs for restart orders are part of the switchgear control function

6. Generator shutdown and tripping
Generator shutdown and tripping involve:
tripping of the circuit breaker connecting the machine to the network (1)
tripping of the excitation circuit breaker (2)
shutdown of the prime mover (3).
The combination of these three orders determines four types of shutdown and tripping orders:
total shutdown (1,2,3), often referred to as simultaneous tripping
generator tripping (1,2)
generator separation (1)
sequential tripping (1,2,3 sequentially).

7. Generator shutdown and tripping Genset shutdown
The genset shutdown function, only present in generator applications, is used for mechanical shutdown by shutting down the prime mover and electrical shutdown by tripping the generator.
Genset shutdown is a control logic function which may be used to include or exclude protection function action in conjunction with genset shutdown. This operation may be disabled.

8. Generator shutdown and tripping Genset shutdown
Genset shutdown may be initiated in the following ways:
by a shutdown order
by delayed protection functions
protection functions unrelated to circuit breaker position:12, 21B, 24, 27TN, 32Q, 40, 51V, 64REF, 67, 67N, 81L, 87M, 87T
protection functions dependent on circuit breaker position: 50/51, 50N/51N, 59N. The time-delayed, non-memorized outputs of these protection functions trigger shutdown only if the circuit breaker is open
by logic equations

9. Generator shutdown and tripping Genset shutdown
Participation in the function is to be set individually in the protection function setting tabs of the SFT2841 software for each protection unit that can take part in genset shutdown.

10. Generator shutdown and tripping De-excitation
The de-excitation function, only present in generator applications, is used to quickly cut off the power supply to an internal fault when the generator is disconnected from the network.
De-excitation is a control logic function that may be used to include or exclude protection function action. This operation may be disabled.

11. Generator shutdown and tripping De-excitation
A de-excitation order may be initiated in the following ways:
by a shutdown order
by delayed protection functions
protection functions unrelated to circuit breaker position:12, 21B, 24, 27TN, 32Q, 40, 51V, 64REF, 67, 67N, 81L, 87M, 87T
protection functions dependent on circuit breaker position: 50/51, 50N/51N, 59N. The time-delayed, non-memorized outputs of these protection functions trigger de-excitation only if the circuit breaker is open
by logic equations

12. Generator shutdown and tripping De-excitation
Participation in the function is to be set individually in the protection function setting tabs of the SFT2841 software for each protection unit that can take part in genset shutdown.

13. Generator shutdown and tripping
Add the outputs for the genset shutdown and de-excitation functions to the control matrix.

14. Automatic transfer Objectives
Automatic transfer is used to increase the continuity of electrical power supply:
to automatically replace a failing power supply,
or to temporarily transfer the load to another branch of the power supply system for maintenance operations.
An operating configuration is chosen as of the design of the installation according to technical and economic criteria.
The chosen transfer principle calls for the installation of breaking cubicles and voltage sensors.
A ladder diagram is created to control the transfer of breaking devices (circuit breakers, contactors or switches) and checking is done to help with the manual return to the usual operating position.
The coupling of power supplies (parallel-connected) is a technical improvement which reduces disturbances for users at the time of the return to normal operation. Generally speaking, the coupling operation, when possible, only lasts for a short time.

15. Automatic transfer Description
The Sepam series 80 substation, transformer, busbars and generator applications contain preprogrammed logic schemes that cover the majority of configurations found in MV or LV installations.
1 out of 2 sources is closed:
There are 2 possible power supplies (one normal and one backup) on the same busbars. Just one of them supplies the busbars. Transfer consists of switching completely to the other source.
2 out of 3 circuit breakers are closed:
2 power supplies are connected to 2 separate busbars, which may or may not be coupled by a coupling circuit breaker. Each source is capable of supplying on its own all of the loads of both busbars. This is why there are some installations with just one power supply and coupling closed and others with 2 power supplies and coupling open.
An automatic load shedding system is sometimes associated with the «backup» power supply.
When there are 2 independent sources, a synchro-check device (ANSI 25 function) is required to enable parallel connection (coupling of sources). This function is only used for the return-to-normal operation.

16. Automatic transfer: «One out of two» transfer (no coupling breaker)
Operating position
After transfer
Transfer !
1) In the normal operating mode, only one power supply is closed. The other one is on standby. This can be a generator or the same line, separated upstream.
2) The loss of voltage or tripping by inter-tripping (fault upstream) trigger the tripping of the supply circuit breaker. The transfer is activated.
3) If all the conditions are met on the opposite circuit breaker (ready to close, correct voltage, etc.), it closes and the busbars are supplied again by this source.

17. Automatic transfer: «One out of two» transfer (no coupling breaker)
Operating position
Return of source
Manual return with or without coupling
Coupling with or without ANSI 25 ! 2 5 2 5 N O

18. Automatic transfer: «Two out of three» with coupling open
Operating position
After transfer
Transfer !
1) In the normal operating mode, both power supplies are closed. Coupling is Normally open.
2) The loss of voltage or tripping by inter-tripping (fault upstream) trigger the tripping of the corresponding breaker (for example, in the diagrams, the power supply on the left).
3) The transfer is activated and the coupling breaker closes. The busbars are supplied again by this source.
N.B. Since the function is symmetrical, the operation described is identical for tripping of the source on the right.
It is important for each power supply to be capable of withstanding the load on its own. Otherwise, a load shedding system may be activated at the same time as the transfer.

19. Automatic transfer: «Two out of three» with coupling open
Operating position
Manual return with or without coupling
Return of source !
Coupling with or without ANSI 25 N O 2 5
The return without coupling triggers another disconnection of the half-busbars (here the busbars on the left) and therefore a disturbance for the users.
The return with coupling is "transparent" for the users, but calls for monitoring of the 2 sources, to avoid problems such as:
de-synchronization, reverse power, upstream fault, fast energy transfer, etc.

20. Automatic transfer: «Two out of three» with coupling closed
Operating position
After transfer
Transfer !

21. Automatic transfer: «Two out of three» with coupling closed
Operating position
Return of source
Manual return with or without coupling !
Coupling with or without ANSI 25 2 5 N O

22. Automatic transfer Implementation in SFT2841
First operation: activation of predefined control logic Tr
Latching of close order
Stabilization of the difference between the 2 sources
1) Closing with synchro-check is used for the coupling of two sources for the transfer (voluntary manual control) and the return (return to the normal operating scheme).
2) The order latching time is useful when the 2 sources are in the process of synchronizing. Closing takes place during this time interval.
3) The synchronization confirmation time is short for the coupling of 2 variable sources and may be 2 to 3 s for the coupling of 2 lines from the same network (since, in theory, there shouldn’t be any difference).
4) This time (tr) is applied after the return of voltage to the NC source to enable a return to normal.
5) This is where the configuration is chosen according to the substation busbars. 1/2: one out of two breakers is closed, or 2/3: two out of three breakers are closed.
Type of transfer
Acknowledgment of the
“close enable (ANSI 25)” input

23. Automatic transfer Implementation in SFT2841
Description of
standard assignments
- compulsory ____
- optional
To record input and
output numbers

24. Automatic transfer Implementation in SFT2841
Second operation:
standard assignment
and activation of the use
of output relays
This input can be connected to one
of the outputs of the MCS025
synchro-check module
Third operation:
add, cancel or reassign inputs
according to the configuration, habits and operating requirements.
Example: - no coupling, - manual control….

25. Automatic transfer Implementation in SFT2841
Fourth operation:
confirm and set the thresholds of the protection functions used by the transfer function.
Example:
27-1 (20%Un) to activate transfer
59-1 (90%Un) to enable a correct return to normal voltage
No latching
No tripping of CB

26. Automatic transfer Implementation in SFT2841
N.B. No latching or tripping

27. Automatic transfer Implementation in SFT2841
N.B. No latching or tripping
The messages linked to the 59-1 threshold must be deleted or else it will appear continuously.
Delete standard «overvoltage» messages

28. Automatic transfer Implementation in SFT2841
Fifth operation:
assign logic to outputs
for interconnection with
other cubicles and indications.
Tripping by automatic transfer: this refers to the tripping of the circuit breaker by one of the transfer conditions.
Tripping by 2/3 or 1/2 logic: NO circuit breaker tripping order.

29. Automatic transfer Implementation in SFT2841
Sixth operation:
Delete the standard
«overvoltage» messages for 59 -1

30. Automatic transfer A few comments
Installations are symmetrical, so ladder diagrams in Sepam units may be identical,
The selector designating the «NO» normally open circuit breaker is used to create the usual operating configuration and therefore differentiate the operation of automatic transfer ladder diagrams.
Not all controls are compulsory.
The inputs (compulsory or optional) have a default value in the ladder diagrams. This must be taken into account since when they are declared in Sepam, they become active in the ladder diagrams.
Internal variables (for example: V-trans-on_flt, V_close_NO_ord...) are available for «remote control» of transfer and the creation of partially or totally specific ladder diagrams.
The «equation editor» and «Logipam» tools provide this adaptation flexibility.

31. Capacitor bank switchgear control Objective
The control logic embedded in the Sepam C86 may be used to protect and control a circuit breaker and 1 to 4 capacitor bank switches.
The capacitors banks may be star-connected or delta-connected.
In the case of star-connection, Sepam provides short-circuit protection of the link to the capacitor bank steps and monitors each link between the 2 stars of each step (fault = unbalance current).
In the case of delta connection of each capacitor bank, the Sepam C86 mainly protects against short-circuits (there is no need for a link between capacitor banks).
Voltage and frequency monitoring, as well as adaptive thermal overload protect the capacitors against the destructive effects of overvoltage and harmonic frequencies (number 13).

32. Capacitor bank switchgear control Description
Circuit breaker control is linked to capacitor bank control
voluntary manual control triggers, first of all, the staggered opening of capacitor bank step switches, followed by the opening of the circuit breaker.
When a fault occurs, the circuit breaker opens the circuit and then orders the simultaneous opening of all the capacitor step switches.
Position matching is monitored for each breaking device.
In «automatic control» mode, an external reactive-energy regulator can control the use of the capacitor bank steps.

33. Capacitor bank switchgear control Implementation in SFT2841
The «capacitors step ratio» is the lowest capacitive value of one of the capacitor bank steps.
The other steps are expressed as multiples of this value. By combining the closing of different steps, it is possible to progressively stagger the value of the capacitance to be connected to the network.
e.g. The capacitor bank value is 42KVAR, i.e. three steps with a capacitor step ratio of 1,2,3, so the capacitor step ratio value is 42 divided by (1+2+3) = 7KVAR.
Step 1 = 7KVAR, Step 2 = 14KVAR and Step 3 = 21KVAR.
Combinations can be made to obtain:
1, 2, 3, 4, 5 and 6 times the lowest value of step 1.
In other words: 7, 14, 21, 28, 35 and 40KVAR.
First operation:
Set the number of capacitor steps
according to the installation,
the connection and capacitor step ratios*

34. Capacitor bank switchgear control Implementation in SFT2841
Second operation:
select circuit breaker control
and capacitor step control.
This is the capacitor discharge time (given by the manufacturer)
These times are used to stagger the
opening of the steps.
The outputs assigned to capacitor bank control should not be set up as «pulse» to acquire the value of this pulse order.
To adapt control* to different
breaking devices.

35. Capacitor bank switchgear control Implementation in SFT2841
The outputs dedicated to capacitor bank control are set up as «latched».
(i.e. not pulse)
Third operation:
assign the inputs and confirm the outputs.
e.g. 3 steps and manual or automatic
control possible by external reactive-energy
regulator.

36. Capacitor bank switchgear control Implementation in SFT2841
Fourth operation:
confirm and set the protection
functions.
Change the messages
when required.

37. Capacitor bank switchgear control Implementation in SFT2841
Fifth operation:
assign the outputs to control
logic and indication.

38. Capacitor bank switchgear control A few comments
Internal variables are available for «remote control» and the creation of partially or totally specific ladder diagrams.
The «equation editor» and «Logipam» tools provide some adaptation flexibility.