The Alstom MVAA21T1BA0549A is a high-speed auxiliary relay designed for use in protection and control schemes. As part of the MVAA family, it acts as a robust interface to multiply contacts, provide galvanic isolation, and handle high-current tripping duties within power system environments.
Product Parameters (Datasheet)
- Model Number: MVAA21T1BA0549A
- Relay Type: MVAA (Multi-contact Auxiliary Relay)
- Configuration: MVAA21 (Standard dual-element or multi-contact architecture)
- Rated Voltage (Vx): 110/125 V DC (Specified by the “0549A” suffix)
- Contact Arrangement: Multi-contact (typically 4 to 8 contacts, configuration dependent)
- Operating Time: Standard speed (typically 15-25ms)
- Reset Type: Self-reset (Standard for MVAA21 series)
- Mounting: Draw-out case, Size A1
- Degree of Protection: IP50 (Case), IP20 (Terminals)
- Burden: Low burden on the DC battery system
Country of Origin
This protective component was manufactured in the United Kingdom by Alstom Grid (formerly GEC Alsthom and later integrated into GE Renewable Energy).
Application Fields
The MVAA21T1BA0549A is a staple in substation automation and industrial power plants for:
- Contact Multiplication: Expanding a single protection signal to trigger multiple actions (e.g., tripping, alarming, and SCADA logging).
- Interposing Logic: Providing isolation between sensitive electronic circuits and high-voltage primary equipment.
- Alarm Schemes: Managing local flag indications and remote alarm contacts.
- Control Interlocks: Facilitating complex interlocking logic between circuit breakers and isolators.
Product Usage Instructions
- Mounting: Install the case into the panel cutout and ensure the earth terminal is connected to the panel ground.
- Chassis Insertion: Slide the relay chassis into the case. Ensure the locking handle is fully engaged to establish electrical contact with the rear terminal block.
- Wiring: Connect the 110/125V DC supply and the initiation signals according to the terminal diagram located on the side of the relay.
- Commissioning: Verify the “Pick-up” and “Drop-off” voltages using a secondary injection test set to ensure they fall within the specified tolerances for the 110V DC rating.
- Maintenance: The MVAA series is virtually maintenance-free, but periodic visual inspection of the contacts for pitting or carbon buildup is recommended in high-cycle applications.
Product Technical Description
The MVAA21T1BA0549A utilizes a classic attracted-armature design optimized for long-term reliability. Unlike tripping relays (like the MVAJ), the MVAA is generally used for auxiliary logic where extreme speed (<10ms) is not the primary requirement, but high contact reliability is paramount. The “BA” and “0549A” codes indicate the specific coil winding for 110/125V DC operation and the specific contact material/stacking configuration. This relay is engineered to operate reliably even in the presence of DC ripple or slight voltage fluctuations common in substation battery banks.
Q&A (Common Questions)
Q: What is the difference between MVAA and MVAJ relays? A: MVAA is a general-purpose auxiliary relay (often self-reset), while MVAJ is a high-speed tripping relay (often hand or electrical reset) designed specifically to trip circuit breakers.
Q: Can this relay be used with AC voltage? A: This specific model is wound for 110/125V DC. Using it with AC voltage will cause the armature to chatter and may damage the coil.
Q: Is it safe to remove the relay from the case while the system is live? A: Yes, the draw-out design allows the relay chassis to be removed without disturbing the external wiring. However, ensure that removing the relay does not inadvertently disable critical protection paths.
Q: How do I know if the relay has operated? A: Depending on the specific configuration, the MVAA may include a mechanical flag (indicator) that drops when the relay is energized.
Similar Model Recommendations
- Alstom MVAA11 (Single-element version)
- Alstom MVAA22 (Alternative contact configuration)
- Alstom MVAJ21 (High-speed tripping equivalent)
- Alstom MVAW (Time-delay auxiliary relay)
- GE/Alstom MMLG (Associated test blocks for relay testing)
For technical support and inventory availability of the Alstom MVAA21T1BA0549A and other protection modules, please visit our digital catalog.
