Main system design
The OLC is based on inductive series compensation by
means of three discrete, mechanically switched air core
reactors, rated at 12 Mvar (2.6 Ω/phase), 24.5 Mvar (5.2 Ω/
phase), and 48 Mvar (10.3 Ω/phase), controlled to achieve a
desired total level of compensation. The reactor system comprises
several compensation steps allowing for eight different
settings following a digital control philosophy, covering the
rated compensation range.
The device incorporates a high-speed response control system,
capable to respond to external reference signals (sent by
the control system or the grid operator) and to measurements
and/or alarms from the system (overloadings).
The OLC is controlled by a micro-processor based control
system. The control system is based on the ABB MACH 2
concept, built around an industrial PC with add-in circuit
boards and I/O racks connected via standard type field
buses. Dedicated voltage and current transformers provide
the control system with network variables employed in the
OLC control.
The control system provides facilities for OLC control either
from an Operator Work Station (OWS) in the OLC control
room or remotely via a GWS in communication with the
SCADA system of REE.
Two control modes are available:
−− Closed-loop control, where an active power limit, P-lim,
or a fixed power value, P-set, are set by the grid operator,
whereupon the required level of compensation is determined
by the control system.
−− Open-loop control, where the compensation steps are set
manually by the grid operator (Impedance setting, Z-set, or
Maximum compensation mode, Z-max).
In addition, there is Emergency Control (P-emerg) to provide
the line with back-up overload protection.
An impedance controller integrates all of the above control
modes inside MACH 2.