PRISMIC® T20 Power System Stabilizer PRODUCT SPECIFICATION Introduction Power System Instability Power system studies and many utility regulations require additional excitation system control functionality to ensure that generators contribute to power system stability. Power system oscillations typically range from 0.1 to 3.0 Hz in frequency and are commonly characterised as inter-area, inter-unit or local modes of oscillation. This functionality can be provided by power system stabilizers (PSS) such as the BRUSH PRISMIC® T20. Power fluctuations are directly related to the rotor angle oscillations of a synchronous generator. Power system stabilizers act on the excitation controller or AVR to adjust the generator excitation to help reduce these rotor angle oscillations. The PRISMIC® T20 is a microprocessor based dual-input power system stabilizer according to the IEEE 421.5 PSS2B model. The stabilizer monitors generator terminal volts and current, from which the operating variables of speed and electrical power are derived. The output of the T20 provides a bias to the reference signal in the AVR. This provides damping of power system oscillations by adjusting the generator field current. The T20 is a compact unit with a steel enclosure designed for securing to a cubicle mounting plate. It can be used as a retrofit unit as well as being incorporated into new systems. The T20 is suitable for connection to most automatic voltage regulators for synchronous generators, with either brushless or static excitation systems. It offers easy connection to any analogue or digital AVR that has the capability to accept a bipolar DC signal from a PSS. It is also possible to transfer the bias signal of the PSS to an AVR via a CAN-bus interface. The user friendly, password protected, Windows based human machine interface (HMI) software, accessed via an RS232 port, ensures the T20 can be fully commissioned in any location. Key Features • • • • • • • • • • • • • • • • Digital design. Uses integral of accelerating power. Based upon IEEE 421.5 PSS2B model. Signal conditioning to minimise erroneous bias signal to the AVR. Uses frequency behind generator reactance as speed signal. Configurable gain setting. Contains 3 lead/lag stages. Isolated PSS output with clamp for protection. Contains diagnostic and monitoring circuits - indications available remotely via HMI, and locally via LEDs on the unit. Analogue output port and CAN-bus interface to AVR. PSS can be disabled via hardware and software. Windows HMI commissioning software. Data recording facility with automatic and manual triggers. 50 and 60 Hz operation. CE compliant. Suitable for brushless and static excitation systems.

f + sTW1 sTW2 1 1+sTW1 1+sTW2 1+sT6 + ∑ N 1+sT8 (1+sT9) M VST MAX + - ∑ KS1 1+sT1 1+sT2 1+sT10 1+sT3 1+sT4 1+sT11 VST MIN Range of settings KS3 P sTW3 sTW4 KS2 1+sTW3 1+sTW4 1+sT7 T1 T2 To IEEE 421.5-2005 standard model PSS2B T 3 T4 PRISMIC T20 block diagram T11 Interfacing to the T20 • • • Data Logging 0.00 to 5.00s 0.00 to 5.00s 0.00 to 5.00s 0.00 to 5.00s 0.00 to 5.00s M N = 1 to 5 = 1 to 2 VST MAX = 0 to +100% VST MIN = 0 to -100% The monitoring circuit in the T20 disables the unit under the following conditions: • Frequency outside acceptable limits. • T20 output exceeds a pre-set level...