Transformer Core Clamp Online Monitoring System Selection Guide and Core Indicators
Date: May 26, 2026, 02:12:02
- Sensor accuracy is key: The measurement accuracy of zero-flux current transformers directly determines whether the system can accurately detect changes in ground currents in the milliampere range, which is the primary consideration when selecting a core monitoring system.
- A range that balances breadth and depth: Since it must be capable of measuring normal ground currents in the milliampere range while also covering fault loop currents in the ampere range, a wide dynamic range is essential.
- Communication Protocol Matching Site: Modbus is suitable for retrofitting existing substations, while DL/T860 is suitable for new smart substations. Before selecting a model, verify the type of communication network used in the substation.
- Installation Compatibility: Available in wall-mounted and rack-mounted configurations; the wall-mounted model (IP55) is suitable for outdoor installation, while the rack-mounted model (IP30) is suitable for indoor installation in control cabinets.
1. Selection of core indicators
| norm | fundamental requirement | Preferred Criteria |
|---|---|---|
| Current measurement range | 1 mA to 10 A | Covers a wider range, accounting for both normal and fault currents |
| Measurement accuracy | ±51 TP3T + 1 mA | Higher accuracy and superior resolution in the low-current range |
| Number of channels | 2-channel (core + clamp) | Expandable to 4 or more channels |
| communication protocols | Modbus RTU | Modbus and DL/T860 Dual Protocol |
| protection class | Wall-mounted IP55 / Rack-mounted IP30 | Meet the environmental protection requirements of the installation site |
2. Detailed Explanation of Selection Criteria
2.1 Sensor Solutions—Zero-Flux is the Preferred Choice
The key to monitoring core ground current lies in measurement accuracy in the low-current range. Zero-flux current transformers, through their specialized magnetic circuit design and active compensation technology, significantly outperform traditional current transformers when measuring low currents in the milliampere range. When selecting a model, focus on the sensor’s measurement accuracy and temperature drift characteristics in the low-current range (1 mA to 100 mA).
2.2 Should the current-limiting function be selected?
Some core monitoring systems incorporate current-limiting devices—when ground current exceeds a preset threshold, a current-limiting resistor is automatically inserted into the ground loop. This feature is suitable for substations with limited maintenance personnel, where it may not be possible to promptly schedule a power outage for repairs after an anomaly is detected. The current-limiting device is an auxiliary function and cannot replace fault resolution.
2.3 Local Display and Remote Monitoring
The system can be equipped with a local display screen to allow inspection personnel to view real-time data, while simultaneously transmitting the data to the backend via a communication interface. For unmanned stations, remote monitoring is essential; for manned stations, the local display enhances inspection efficiency.
3. Frequently Asked Questions FAQ
3.1 Q: Is it necessary to choose a core monitoring system with current-limiting functionality?
A: Not necessarily. If a substation has a robust operation and maintenance management system and can promptly arrange for a shutdown to address any abnormalities upon detection, basic monitoring functions are sufficient. Current-limiting functions primarily serve as a supplementary safeguard for sites where response times cannot be guaranteed.
3.2 Q: Are two channels enough? When do you need more channels?
A: Standard transformer cores and clamps are each grounded on a separate channel, so two channels are sufficient. If the transformer has multiple core sections or separate grounding wires for individual clamps that need to be monitored separately, more channels will be required. A large three-phase five-column transformer may require four channels.
3.3 Q: Can the core monitoring system share the same backend with partial discharge and oil chromatography systems?
A: Yes. As long as the communication protocols are compatible (both support Modbus or DL/T860), the various monitoring subsystems can be integrated into a unified monitoring platform. Multidimensional data from the same platform facilitates correlation analysis and comprehensive diagnostics.
Disclaimer: The content of this article is for technical exchanges and reference only, and does not constitute any form of procurement commitment or contract offer. Product technical parameters, configuration programs and prices are subject to the actual signed contracts and technical agreements. The technical data and cases involved in this article are from public information and engineering practice, if updated without notice.
Need advice on selecting an online monitoring system for transformer core clamps? Contact Innotongda for a customized solution. Service Hotline: 13959168359 (also on WeChat).
