SVC for cost-effective replacing of local generation with remote power import
In 2002, ABB commissioned a total of three Static Var Compensators (SVC) in the national power transmission grid of Sonelgaz in Algeria, one at Naama substation and two at Bechar. All three SVCs are of identical rating, -10 / +40 Mvar at 220 kV. In the grid, there is a 500 km, 220 kV single circuit overhead transmission line for feeding of a remote load in the western parts of the country, thereby replacing local diesel and gas turbine generation feeding loads in Bechar since the beginning of the nineties which were shut down during 2002. Two 220/60 kV substations, one intermediate (Naama) and one at the end of the line (Bechar) were equipped with SVC to serve the following purposes: − − To give the power transmission system reactive power support in order to maintain a stable voltage during normal, daily operation. − − To yield dynamic voltage control during energizing of the 220 kV line as well as maintain a stable voltage in the system under various operating conditions. In particular, to prevent voltage collapse and system instabilities during transient and fast changing voltage conditions in the system. The loads taken off the 220 kV system are in the order of 12 MVA at Naama and 35 MVA at Bechar.
At Naama, one SVC has been installed. At Bechar, two identical SVCs connected to the same 220 kV bus have been installed. They can be operated together in joint control, as well as individually. Main circuit design The three SVCs all have identical main circuit design, each with an overall dynamic range of 10 Mvar (inductive) to 40 Mvar (capacitive) at 220 kV. This dynamic range is attained by means
Algers SONELGAZ Naama -10/+40 Mvar 220 kV
ALGERIA
SONELGAZ Bechar 2 x (-10/+40 Mvar) 220 kV
220 kV
of a Thyristor-controlled reactor (TCR) rated at 25 Mvar, a Thyristor-switched capacitor also rated at 25 Mvar, and a 5th Harmonic filter rated at 15 Mvar. By a combination of phaseangle control of the TCR and switching of the TSC, the SVCs can be continuously controlled over their entire range. Control system The SVC control system is built up by a microprocessor based computer function that constantly monitors the status of the SVC reactive output and status of switching devices. In normal operation the SVCs are voltage controlled. The operator sets a certain 220 kV bus voltage level and the SVCs produce sufficient reactive power to maintain this desired voltage. In Bechar, the two SVCs are normally operated together in joint control. In this mode of operation, the voltage reference settings of both SVCs are in unison. Each SVC can be operated individually, as well, as previously stated.
TCR 25 Mvar
TSC 25 Mvar
5 th 15 Mvar
Single-line diagram
Over- and undervoltage strategies At system overvoltages and undervoltages, different actions will be taken by the SVC. Undervoltage strategy If the primary voltage, due to some fault on the 220 kV line, drops to a low value, the normal voltage control will control the SVC to full capacitive output, to support the system voltage. For very deep voltage drops, however, a special undervoltage strategy is applied. If the system voltage drops below the adjustable level 0.6 pu, the TSC is switched off and the TCR is controlled to full conductivity, i.e. to an overall SVC output of 10 Mvar inductive. Overvoltage strategy The TCR valve is designed to be controllable up to 1.3 pu primary voltage. If the voltage exceeds this value, the TCR valve is controlled to fully conducting, and the TSC is automatically switched out. If the primary voltage is above 1.2 pu for more than one second, an SVC trip is initiated.
Operator Interface
Main Circuit
VarMACH Switch Control Unit & Binary I/O
MIMIC Panel Annunciator Panel
Var Control Computer
Data Acquisition Unit TSC Supervision Unit
Synchronizing Unit Control Pulse Generator
Valve Base Electronics
Control system overview.
Number of SVCs per substation Naama 1 Bechar 2 For more information please contact: ABB AB FACTS SE-721 64 Västerås, SWEDEN Phone: +46 (0)21 32 50 00 Fax: +46 (0)21 32 48 10 www.abb.com/FACTS
Technical data (for each SVC) Controlled voltage SVC rating Control system Thyristor valves
220 kV 10 Mvar inductive to 40 Mvar capacitive. Three-phase symmetrical voltage control by means of a closed-loop regulator. Water cooled, with indirect light firing.
A02-0183 E, 2011-01, Elanders Sverige AB
45 MVA