Product Overview

The MVAJ105RA0802A (MVAJ105RA0802A) is a high-speed, hinged armature tripping relay belonging to the renowned MVAJ product range. This module acts as the critical interface between primary protective relays and circuit breaker trip coils in high-voltage substations and industrial power networks. Designed for absolute reliability, the MVAJ105RA0802A ensures that trip commands are executed with sub-millisecond precision and minimal contact bounce. By providing a rugged and flexible link in the protection chain, this relay prevents equipment damage and enhances the safety of power distribution systems under fault conditions.

Technical Configuration (Deep Dive)

The MVAJ range is engineered to accommodate a variety of complex tripping schemes through its versatile armature design and burden-selection capabilities.

• High-Speed Operation: Utilizes a lightweight, high-performance hinged armature that ensures rapid contact closure, vital for minimizing the duration of electrical faults.

• Selectable Burden: Features an external link connection that allows engineers to select between high and low burdens. The high-burden configuration provides superior immunity to wiring capacitance discharge, preventing nuisance tripping in extensive cabling networks.

• Reset Logic: The RA0802A variant is typically configured with hand or electrical reset mechanisms (depending on internal wiring), providing clear visual indication of a trip event via a mechanical flag.

• Immunity & Security: Built with internal filtering to ensure immunity to AC/DC interference and capacitive discharge from long pilot wires, making it ideal for large-scale utility grids.

Technical Specifications

Technical FAQs

Q1: How does the MVAJ105RA0802A prevent accidental tripping from stray signals?

A1: The relay can be configured in a high-burden mode, which requires a higher energy threshold to operate. This effectively filters out noise and capacitive discharges common in long-distance control wiring.

Q2: What is the significance of the "RA" code in the model number?

A2: The "RA" designation refers to the specific contact arrangement and reset logic. In this series, it signifies a relay designed for multi-contact tripping with specific reset capabilities for fault signaling.

Q3: Does the mechanical flag require manual intervention after a fault?

A3: Yes, for hand-reset models, the mechanical flag must be manually reset by an operator after the fault is cleared to acknowledge the trip event and restore the relay to its ready state.

Engineering & Installation Guide

• Contact Burden Setting: During commissioning, verify the external link position. Use the "High Burden" setting if the relay is located at a significant distance from the protective device to negate the effects of cable capacitance.

• Mounting Orientation: The MVAJ105RA0802A must be mounted vertically on a vibration-free panel. Any significant tilt can affect the gravitational balance of the hinged armature, potentially altering the operating speed or sensitivity.

• Tripping Coil Compatibility: Ensure the breaker trip coil's current requirements do not exceed the relay’s contact rating. For multiple trip coils, verify that the parallel current remains within the 10 A (short-term) thermal limit of the relay contacts.

Engineering Advantages

The ALSTOM MVAJ105RA0802A is celebrated for its "set and forget" reliability. With its minimal contact bounce and high-speed response, it protects circuit breaker coils from prolonged energization. The module's design is compliant with the highest international protection standards, ensuring that it remains operational even after years of inactivity in a substation cabinet. Its compact footprint allows for high-density installation, enabling complex multi-contact tripping schemes to be housed in standard protection racks without excessive space requirements.