SPS – Parallelism Supervisor
The Synchronous Parallelism Supervisor SPS is a device developed by Treetech for control and supervision of parallel operation of power transformers equipped with a load tap changer. The SPS incorporates functions of a range of equipment that, in the past, were used to control parallel transformers, such as position indicators, auxiliary relays for electro-mechanical logic, selector switches Master/Follower/Individual, Manual/Automatic, Local/Remote and Raise/Lower, among others. The SPS significantly reduces command wiring needs as well as the number of components. The result is a considerable increase in the overall reliability and reduced labour times for installation and testing, in addition to simplifying maintenance.
The device’s operation philosophy is based on the Master-Follower method, in which one of the transformers is chosen as the Master, and the remaining units are Follower or Individual (not in parallel). Due to the digital techniques of the SPS all the tap changes performed by the master transformer is also initiated simultaneously in the follower transformers, thus preserving the same position in all transformers and avoiding current circulating among the windings in parallel. In case of discrepancy between taps of transformers in parallel, as well as the occurrence of any other error (invalid programming, failure in serial communication, etc.), the operation of tap changers is blocked.
The SPS can control up to six three-phase transformers in parallel, or up to six banks of single-phase transformers, that is, 18 transformers in total. The equipment also performs parallel operation of combinations of three-phase transformers and banks of single-phase transformers.
Main Features:
• IED (Intelligent Electronic Device) designed specifically for substation yard conditions (electromagnetic interference, extreme temperatures), suited for integration of supervision or monitoring systems by way of RS485 port (Modbus standard, DNP3.0 optional);
• Modular system that can be configured in accordance with application needs. Configurable transformer type: three-phase or bank of single- phase transformers;
• Selections Master/Follower/Individual, Local/Remote, Manual/Automatic and Raise/Lower commands performed directly on the front panel or through external dry contacts;
• Intelligent Position Measuring: compensation for resistance of measuring cables, failure detection and alarm for failed position measuring, due, for example, to bad contacts on the potentiometer sensor or connection cables. Option for position measurement input by current loop;
• Selectable position indication type on the display: simple numeric (ex.: 1…33), bilateral numeric (ex: -8…0…+8) or alpha-numeric (ex.:8L…N…8R). Programmable total number of positions and resistance of the potentiometer sensor allowsadaptation to all models and manufacturers of LTCs. Easy to visualize LED display;
• Analog output for remote position reading. User selectable output range: 0…1, -1…1, 0…5, -5…5, 0…10, -10…10, 0…20, -20…20 or4…20mA);
• Four output relays for indication of alarms and states;
• Self-diagnosis: two micro-controllers with reciprocal supervision for detection of failures. Total absence of mechanical parts for parameter definition and calibration.
Expansion Signalling Contacts
If necessary, it is possible to expand the number of signalling contacts of the paralleling system using the Control Module DM3 in its special version named DM3-SP2.
The expansion of the signalling contacts can be especially useful when the SPS is used with a three-phase transformer, because in this case only 4 signalling contacts are available per three-phase unit.
The DM3-SP2 module has 8 Normally Open output contacts grouped in two 4-contact sets. Each set of contacts attends to one three-phase transformer or to one bank, in such manner that each DM3-SP2 module attends up to 2 transformers or banks. Each 4-contact set has the following fixed signalling functions: Master, Follower, Individual and Remote modes.
Detailed information can be found in the specific MD3-SP2 documentation.
Potentiometric Position Sensor Magnetic type
The majority of recent load tap changers, and many of the old ones, are supplied from the factory with a potentiometric position transmitter or dry contacts that allow the creation of the transmitter by means of the appropriate installed step resistors.
However, for tap changers that do not have any of these alternatives, Treetech can provide magnetically operated potentiometric position transmitters, without mechanical contacts, for easy installation in older equipment.