1. Using IEC 61850 Analogue GOOSE Messages for OLTC Control of Parallel Transformers
Zoran Gajić, ABB SA Products, Sweden
Samir Aganović, ABB SA Products, Sweden
Josip Benović, TSO (HEP), Croatia
Sergio Gazzari, ABB Croatia
Goran Leci,
Končar-Power Plant and Electric Traction Engineering Inc., Croatia

2. 1. Introduction 2. Parallel control (circulating current method) 3
1. Introduction 2. Parallel control (circulating current method) 3. Automatic tap changer controller (ATCC) 4. Inter IED communication (GOOSE messages) 5. Conclusion

3. 1. Introduction
Automatic voltage control can be either for single transformer or for parallel transfomers
Voltage automatic control function is designed to
maintain service voltage at the LV side of a PT within given limits around a set target voltage Uset
Voltage control function measures the magnitude of the LV side busbar voltage UB and compares it to the Uset

4. Voltage scale for control actions
If the voltage UB is measured to be outside the
deadband (U<U1 or U>U2), command sequence starts and after time delay has elapsed, appropriate raise or lower command will be issued

5. Parallel control of PTs means control of two or more PTs
Introduction
Parallel control of PTs means control of two or more PTs
connected to the same busbar on LV side
Parallel control can be made by three alternative methods:
- reverse reactance method,
- master-follower method*,
- circulating current method*
* Requires communication among the voltage control functions on the
PTs in parallel group

6. 2. Parallel control with the circulating current method
PT with a higher no-load voltage on LV side (higher tap
position) will produce circulating current, while other one
with lower no-load voltage will receive circulating current
When load is put on the PTs, the circulating current will
remain the same, it will be superimposed on the load
current in each PT

7. Parallel control with the circulating current method
Circulating current method aims to minimize the circulating
current at the given voltage target value and ensures total
reactive load is shared between parallel PTs in proportion
to their rating

8. Parallel control with the circulating current method
Method requires extensive exchange of data between
the voltage control functions
Summary of required signals to be communicated for
circulating current method:
- measured busbar voltage,
- measured transformer current (real and imaginary parts),
- voltage set point,
- blocked status, control in manual, timer on ...

9. 3. ATCC installation
Two 20 MVA, 110/20 kV, YNd5 transformers with OLTC
Each PT has dedicated IED with integrated protection
and control functions
Automatic control of parallel transformers is done by
circulating current method (∆Isinɸ)
Information exchange between voltage control functions
for PTs in parallel are done by GOOSE messages
in accordance with IEC standard

10. ATCC installation A Automatic control Y Power transformers
IEC defines 91 logical nodes divided into 13 groups:
Logic group
Name L
System logic node P
Protection R
Protection related C
Control G
Generic I
Interfacing and archiving A
Automatic control M
Metering and measurement S
Sensors and monitoring X
Switchgear T
Instrument transformers Y
Power transformers Z
Further power system equipment

11. S/S 110/20 kV Donji Andrijevci – ATCC installation
RET670
87T, 87N,
50/51, 50N/51N, 49,
90 (ATCC), 84 (YLTC)
REB500 BU
21T, 50/51
REX521+SPAZC402
50N/51N

12. Logical nodes ATCC and YLTC
ATCC represents regulator itselfs and integrates
funcionality like:
- voltage measurement and supervision,
- timing, line drop compensation,
- circulating current measurement and supervision etc.
YLTC represents OLTC mechanism and integrates
- tap position reading,
- OLTC mechanism supervision,
- issuing of the manual and automatic raise and lower
commands

13. Logical nodes ATCC and YLTC

14. 4. Inter IED comm. between voltage control functions
GOOSE message is contained by:
- single point status of binary inputs or outputs,
- double point status of control apparatus,
- analogue values (measured voltage, currents, ...)
IEDs send GOOSE messages periodically and multicast in predefined intervals on data change inside associated dataset

15. Inter IED comm. between voltage control functions
IEDs contain GOOSE control blocks with associated datasets
containing XCBR and CSWI which the voltage control function
needs for single/parallel operation

16. Example from PCM600/CAP531

17. Example from PCM600/CAP531

18. Inter IED comm. between voltage control functions
Complete exchange of voltage control function data,
analog as well as binary, is made by GOOSE messages

19. Inter IED comm. between voltage control functions
Voltage control block will send the same dataset, but each of them
will have unique address definitions for GOOSE control block

20. Example from PCM600/CAP531

21. 5. Conclusion
For parallel transformer application, we used circulating
current method (requires comm. between voltage control
functions in parallel group)
Chosen comm. interface is GOOSE interbay communication
based on IEC
Since September 2007 three S/Ss with such control are
in full operation and all engineering process is done by
Končar engineers with Croatian TSO and ABB help

22. Questions?