SDMO RENTAL POWER R550C2 User And Maintenance Manual page 77

Principle of coupling when stopped
- all the generating set power units are switched off,
- starting of all the generating sets,
- when the speed reaches 1450 rpm, activated excitation command on all the generating sets,
- the voltage generated by each generating set increases gradually and the voltage is therefore the same in all generating
sets,
- the generating sets therefore reach 1500 rpm at 400 V 50 Hz.
At the end of global operation, if the power consumed by the installation does not require the operation of all the generating
sets within the power plant, one or more generating sets will be stopped according to the wattmetric control.
Restarting of the generating set (these generating sets) depends on the load and wattmetric control of the load.
However, if a generating set is reconnected to a busbar already subjected to a load, the "recoupling" is carried out in normal
operation and not when the generating set is stopped.
Principle of coupling in normal operation
Coupling in normal operation enables all the generating sets to be coupled (in voltage and frequency) to a busbar supplied by
a generating set designed as master at the output.
A number (1 to 15) is assigned to each Kerys. This number serves solely to establish the IP address of each Kerys for
communication by Ethernet and loading the programs.
A second number (from 1 to 15) is also assigned to each Kerys and defines the priority.
Example: let us assume a plant of 8 generating sets
Gen set
Priority
The numbers on the first line enable the IP address of each Kerys to be allocated. The numbers on the second line define the
priority.Therefore Kerys no. 8 with priority 01 is considered to be the master generating set and closes its flow first. The other
generating sets then synchronise one by one to the central busbar, transmitting the information on voltage, frequency and
phase difference to this busbar (see sketch).
GS1
CB1
Example for 3 GSs:
•
DJ1 (Circuit breaker 1) is closed, the voltage is present on the busbar.
•
Kerys 2 analyses the differences between U2 and U of the busbar before coupling.
• Kerys 3 analyses the differences between U3 and U of the busbar before coupling.
Each Kerys, independently of its neighbour, will close its discharge on the central busbar.
Wattmetric control
The wattmetric control is used when two generating sets are coupled. It provides optimum management of the number of generating
sets operating by constantly analysing the power required by the user.
Let us take the example of a power plant of 4 x 600 kW generating sets.
The threshold setting screen (1-7-3-3) supplies the following data:
Threshold 1 GS => 2 GS
Threshold 2 GS => 3 GS
Threshold 3 GS => 4 GS
The maximum available power is 600 x 4 = 2400 kW. Assuming that a single generating set is operating, we will have the following
sequence in the case of linear progression of the load.
1 2 3
08 07 06
GS2
U1
CB2
75% 450 kW
75% 900 kW
75% 1350 kW
4 5 6
05 04 03
U2
CB3
Busbar U
Threshold 2 GS => 1 GS
Threshold 3 GS => 2 GS
Threshold 4 GS => 3 GS
75/298
7 8
02 01
GS3
U3
30 % 360 kW
30 % 540 kW
30 % 720 kW