Configuration scheme for local discharge monitoring of transformers at different voltage levels

• Voltage level determines risk levelThe higher the voltage level, the greater the hazard of localized discharges, and the higher the requirements for the accuracy and reliability of the monitoring system, the configuration strategy needs to be designed hierarchically according to the voltage level.
• 10kV/35kV Distribution Transformer: the largest number but the importance of a single unit is relatively low, it is appropriate to use economic single-sensor or dual-sensor program, focusing on coverage of high failure or operation and maintenance difficulties in the site
• 110kV City Main Substation: medium to high importance, ultrasonic + high-frequency current dual sensor 4-channel solution is recommended, balancing performance and investment.
• 220kV/500kV Hub Main Substation: The backbone node of the power grid, with a large range of fault impacts, should use ultrasonic + high-frequency current + UHF three-in-one fusion program, leaving no monitoring blind spots

1. Layered configuration strategy

2. Configuration details for each voltage level

2.1 Distribution transformers (10kV/35kV)

Distribution transformers are so numerous and dispersed that it is not possible or desirable to locally monitor each and every one of them on-line. The configuration strategy should be selective deployment - prioritizing installation on critical customer supply transformers, older transformers, and transformers with a history of failures. The solution is based on ultrasonic single sensors, which are the easiest to install and the most economical to invest in. For particularly important distribution transformers can be upgraded to a dual sensor solution.

2.2 Urban substations (110kV)

110kV substations are usually located in urban load centers with large outage impacts. The ultrasonic + high-frequency current dual sensor 4-channel solution is a cost-effective choice. Two ultrasonic sensors are distributed in different directions of the transformer to provide reference for discharge localization, and two high-frequency current sensors are used to monitor the PD impulses of the core and the clamping ground circuit respectively.

2.3 Hub substation (220kV)

The 220kV substation is a hub node of the regional power grid, requiring significantly more comprehensive and reliable monitoring. The three-sensor fusion solution utilizes ultrasonic for localization, high-frequency current for highly sensitive capture, and ultra-high frequency for anti-jamming confirmation, with cross-validation of the three sensors. 6-channel configurations allow for the deployment of sensors at each ground loop and at multiple tank locations.

2.4 Backbone substation (500kV)

The importance of a 500kV substation cannot be overstated - a single main substation outage will affect the safety of the entire regional power grid. In addition to the three-sensor fusion solution, the redundant configuration of key sensors, the integration of local discharge monitoring data into the station-level integrated monitoring platform, and the realization of multi-dimensional co-diagnosis with oil chromatography and temperature monitoring should also be considered.

3. Frequently Asked Questions FAQ

3.1 Q: Is it cost-effective to install local discharge monitoring on distribution transformers?

A: It is indeed uneconomical to install full coverage of all distribution transformers. The recommended strategy is selective deployment - trial installation at key sites first, and decide whether to promote it based on actual results. The lightweight single-sensor solution can already provide basic local discharge warning capability with a reasonable input-output ratio.

3.2 Q. Are dual sensors sufficient for 110kV transformers? Do I need to go to UHF?

A: For most urban 110kV substations, where the electromagnetic environment is within acceptable limits, a dual sensor solution is sufficient. Only if the substation is located near strong electromagnetic interference sources such as broadcasting stations, radar stations, etc., do you need to consider upgrading the UHF solution.

3.3 Q: Is there a difference between the configuration strategy for a new station and an old station retrofit?

A: New construction design stage can be pre-installed in the transformer manufacturing built-in UHF sensors, to achieve the optimal sensor layout. Retrofitting of old stations is dominated by external sensors installed without power supply, and ultrasonic and high-frequency current sensors are not subject to this limitation.

3.4 Q. Can system data from different voltage levels be managed in a uniform manner?

A: Yes. Through a unified integrated monitoring platform and a standardized data upload protocol, the local discharge monitoring data from different sites can be brought together in a regional diagnostic center to achieve centralized monitoring and unified management.

3.5 Q: Are there any recommendations for generic configurations across voltage levels?

A: If you are looking for a configuration with the widest range of applicability, the Ultrasonic + HF Current Dual Sensor 4-channel solution is the option with the widest coverage - providing effective localized discharge monitoring capability for transformers from 35kV to 220kV, with a good balance of price/performance ratio and range of applicability.

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.

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