The parallelism system for power transformers equipped with shunt taps under load has traditionally been done by an electro-mechanic panel, with analog indication of TAP position and manual tap change.…
ELECTRONORTE S.A. – ENSA, a distribution company located in the north Peru, attends more than 256 thousand clients around Lambayeque, Amazonas and part of Cajamarca, decided to change its automatic voltage regulation system, compounded by MK-20 equipment along with SKB-20, installed in two 17,5MVA – 60/10 kV transformers made by ABB at the power substation named Chiclayo Norte
That equipment, which served the power substation for years, was no longer presenting the systems’ expected reliability for the company’s current business model, which seeks more efficiency of the new IEDs – Intelligent Electronic Devices – with less maintenance needed, more monitoring functions and with possibilities of connection to the automation of the substation through serial communication with open protocols.
Additionally, due to the age of these devices, more than 15 years, there were no more spare parts available, maintenance has become expensive and with lingering terms to get back to work.
The changing was made on February 24th 2008, with the presence of the engineer Walter Arenas and the technician Tolentino Ruiz, both from ENSA, and the Logytec SRL engineer Carlos Gonzáles. The operation started at 5h30 a.m., the power shutdown moment of the substation.
The first step was identifying the cables, since the previous system used external contactors to adjust the operation in parallel by circulating current, which increased possible failure spots. This problem was solved with the ARV, once this version performs the adjustment by circulating current upon an intern algorithm without any external contactors needed. This way, the numbers of cables decreases, consequently, the number of failure spots decreases as well.
In addition, AVR relies on six time slots for configuring the regulation. At that case, three of them were configured, at the request of ENSA.
On the other hand, the configuration and communication with the RTU were easily made by the serial port RS-485 and the Modbus open communication protocol.
Another highlight fact is that, before, the operation in parallel by circulating current was done with two devices per transformer, although, with the AVR, only one equipment is required to do the same thing.
Scope of Supply:
– IEDs sensors located in the control panel at the Control Room.
- 02 AVRs – Voltage Regulator Relays with Circulating Current Parallelism;
– Engineering Services and Installations
- Compatibility Study;
- Electric project – Retrofit;
- Removal of existing equipments;
- Installation of AVRs Treetech and commissioning;
- Training for parameterization and operation of installed AVRs.
With the new parallelism system designed with the IEDs of Treetech and with the installation and commissioning by LOGYTEC under the supervision of ENSA, the issues presented in Voltage Monitoring and Transformers Parallelism Systems were solved and the Sub-station is fully operational.
The reduced dimensions of AVR equipments offer space saving in the panel for other modernizations.
The Device – AVR – Automatic Voltage Regulator
In an increasingly demanding market in terms of Quality of Electric Energy, the rules for parameter definition and acceptable supply limits are becoming more stringent. There is a growing need for tools capable of meeting this reality and affording adequate voltage regulation.
Within this context, Treetech’s New Voltage Regulator Relay AVR offers a solution that goes beyond the traditional and well-known “90” relays. The AVR is fitted with unprecedented resources in order to afford better control of load voltage limits, allowing the most stringent requirements to be addressed and met.
The IED performs the “function 90” of voltage regulators, using mathematical models and AI depending on the load curve. It has parallelism control and maintenance of the OLTC management as optional features.