T&D World Magazine

Relays Offers High-Performance Fault Clearance in Electrical Power Line, Cable Protection

AREVA Transmission & Distribution has just launched a new, cost-efficient and user-friendly family of advanced numerical distance and differential protection relays in its MiCOM range. Models exist allowing the user full flexibility to select differential or distance elements alone or both modes of main protection in a single device. Designed for use in electrical power substations, especially for critical transmission lines, the models include versatile characteristics to offer the most reliable and secure fault clearance available in the marketplace. Advanced teleprotection using InterMiCOM64 signaling avoids the need to invest in costly external equipment to transmit end-to-end relaying data.

The distance protection within the family is branded MiCOMho and consists of the existing P443 superset model, specifically designed for subcycle performance, and the new P445 fully-functional, compact model (4U x 40TE/8 in width). Both models are for utility transmission or distribution grids (typically 33 kV to 1 MV) and are particularly designed for high-speed protection resulting in less fault damage and no risk to the stability of the network.

The P443 relay offers a universal selection of “mho” and quadrilateral distance elements, with independent directional ground (DEF) schemes. Delta directional comparison schemes are incorporated, together with single and three pole tripping plus optional autoreclosure. The P445 employs the same enhanced technology, simplified to match the less complex scheme requirements at lower system voltages. Tripping is three-pole, with mho phase fault protection , and ground elements mho or quadrilateral--the latter especially for short line and cable applications.

The advanced differential protection devices are branded the P540 series, with four new models, P543 to P546. Within these four models, the optimum model to match the connectivity requirements of the user’s application can be found. For example, the P545 and P546 offer a greater amount of digital inputs and outputs, for ease of integration in traditional hardwired schemes. The substation topology is catered for too, with the P543 and P545 designed for simple single circuit breaker feeding, whereas the P544 and P546 models are adapted for two breaker feeding arrangements. The latter is true where the topology is double bus, ring bus, or “breaker and a half”.

The new differential protection models include a “Differential CTS” feature (patent pending). CTS denotes current transformer supervision and is the means whereby wiring and connection failures in current transformer circuits will be detected instantaneously. Such high-performance detection means that no wiring failure can risk an unwanted trip, and the availability of the power line is not compromised. The protection performance of the P540 differential devices is enhanced too, as they now contain the same subcycle distance elements as per the P443 MiCOMho.

The range is completed by the InterMiCOM64 integral digital teleprotection system which interacts with the relays by outputting teleprotection messages from relay to relay in record time (5 ms). The feature enables the protection relay to interface directly with the communications channel with either fiber optic links or any of the main multiplexed telecommunications systems, therefore cutting down on costs. It is designed for two terminal or triangulated three-ended schemes.

AREVA T&D designed the range with the user in mind, particularly electricity utilities, to address a gap in the market. All the new MiCOM models are targetted for operators/asset owners; notably for transmission systems and distribution networks.

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