Parallel operation of transformers with system topology

ab

ab

ab

ab

ab

ab

a b

a b

T1

K1 K3

K17 K18

K19 K20

S1

S5 S6

S7

S8

S2 S3 S4

T3

In addition to their principal task, which is toassure constant transformer voltage for a widerange of load conditions, state-of-the-art volt-age regulators are also capable of mapping thetopology of a switching system with its isolat-ing switches and circuit breakers.

Voltage regulators like TAPCON 240are thus capable of taking over the configu-ration of a switching system and adaptingits regulating behaviour to the systems cur-rent switched condition.

At the same time, it also allows theparallel operation of transformers to becontrolled with great ease. A TAPCON 240is capable of controlling up to 16 voltageregulators of the transformers connected inparallel. The exchange of information be-tween the regulators is realized via CANbus and is possible for distances up to2 kilometres.

We have used a very simply andstraightforward configuration example of aswitching system to show you how the soft-ware works during parallel operation withsystem topology.

The example below shows the paralleloperation of two transformers, T1 and T3, ata twin bus-bar with bus-tie circuit breakerand bus-tie disconnector.

Each circuit breaker is represented by aswitching symbol. This circuit breaker S per-mits any switched condition of the systemto be visually displayed.

For this purpose, the feed-in points ofthe 16 transformers possibly connectible arereferred to as K1 16. The designation ofany additional connecting points will beginwith K17.

Each circuit breaker S is equippedwith the connection terminals a and bwhich connects it to the other circuitbreakers and/or transformers present in thesystem.

Parameters Connecting nodes Designation - Transformer 1Designation - Transformer 2Designation - Transformer 3Circuit breaker 1 Terminal a 1Circuit breaker 1 Terminal b 17Circuit breaker 2 Terminal a 1Circuit breaker 2 Terminal b 19Circuit breaker 3 Terminal a 3Circuit breaker 3 Terminal b 18Circuit breaker 4 Terminal a 3Circuit breaker 4 Terminal b 20Circuit breaker 5 Terminal a 17Circuit breaker 5 Terminal b 19Circuit breaker 6 Terminal a 18Circuit breaker 6 Terminal b 20Circuit breaker 7 Terminal a 17Circuit breaker 7 Terminal b 18Circuit breaker 8 Terminal a 19Circuit breaker 8 Terminal b 20Circuit breaker 9 Terminal a 0Circuit breaker 9 Terminal b 0... ... ...... ... ...Circuit breaker 16 Terminal a 0Circuit breaker 16 Terminal b 0

Parameter table of the system topology

Dr. Karsten ViereckHead, Electronics/Monitoring Development Dept.

Parallel operation of two transformers

SYSTEM TOPOLOGY

SYSTEM TOPOLOGY

To make sure the TAPCON 240 is capableof mapping the switched condition of asystem via its binary inputs, the informa-tion as to which terminal clamp is con-nected to which connecting point or feed-in point is laid down in the regulators pa-rameter file.

The example contained herein refersto the parameter table for the 16 circuit breakers max., in whichcase any non-existent circuit breakers aresimply connected to node Zero and dotherefore not register as existent duringthe subsequent program inquiry.

The software of TAPCON 240 nowuses a method remotely reminiscent of thealgorithm of a node tension analysis fordetecting the switched condition of a sys-tem in order to control the transformersparallel operation.

To that end, following an inquiry ofthe circuit breakers by the regulator, thesoftware internally assigns a number toeach closed circuit breaker of the system.By comparing the connecting loads via theclosed circuit breaker, the software estab-lishes a connection matrix which is thenreduced through the comparison of knownconnections. That way, the regulator can

determine without a doubt which of thetransformers are connected in parallel.

The substation topology visualizationsystem realized so far allows the display ofup to six transformers on two displaypages.

These six transformers in turn can beinterconnected into individual groups atthe users discretion.

The transformers represented assymbols are then shown together withtheir respective switched-in-parallel trans-formers on the displays topology pages.

The user has a choice of assigningthe transformer designations himself, in

Topology representation on the TAPCON 240

Transformer designation

Group

the same manner as the designationsfound in his substation. In case a trans-former belongs to a group which is nolonger presentable on the same display, therelated connecting line will stop as a dot-ted line at the edge of the screen.

That is how the TAPCON 240 volt-age regulator elegantly solves the tasks ofidentifying the switched condition of asubstation with its connected transformers,executing the activities required for paral-lel transformer control, and representingthe current system topology on its display.