Transformer oil temperature oil level how to monitor

Transformer oil temperature and oil level monitoring is the most basic and important means to ensure the safe operation of the transformer. Monitoring methods are mainly divided intoConventional mechanical/analog monitoring(for on-site visual readout and foundation protection) andModern online monitoring(for remote centralized control and precise diagnostics).

Below is a detailed breakdown of the monitoring program, covering conventional to high level technical tools.

I. Transformer oil temperature monitoring

Transformer temperature monitoring is usually categorized asTop oil temperaturerespond in singingWinding TemperatureThe

1. Top Oil Temperature monitoring (Top Oil Temperature)

This is the monitoring of the temperature of the upper hot oil layer of the transformer and usually reflects the overall heat dissipation of the transformer.

• Commonly used equipment:

  • Pressure thermometer (BWYseries): This is the most common field instrument. The principle is to use the temperature-sensitive liquid inside the temperature package to expand by heat and drive the pointer to indicate the temperature through the capillary tube.

  • Pt100 platinum resistance: A Pt100 sensor is embedded in the temperature measuring hole holder to convert the temperature into a resistance signal (usually converted to a 4-20mA current signal by a transmitter), which is transmitted to the back-end SCADA system.

• Alarm Logic: Two thresholds are generally set, one forgive a warning(e.g. 85°C), one for(of a circuit breaker or switch) trip(e.g. 95°C).

2. Winding Temperature Monitoring (Winding Temperature)

The windings are the core of the transformer's heat generation and their temperature is usually higher than the top oil temperature. There are two methods of monitoring:

• Traditional “thermal simulation” method (WTI):

  • Principle: It's aindirect measurement. It does not contact the high voltage windings directly, but measures the top oil temperature with aCurrent Transformer (CT) The load current is captured. The current flows through the heating resistor inside the meter and simulates the temperature rise of the windings on the oil superimposed on the oil temperature.

  • Drawbacks: The response is lagging, the accuracy is greatly affected by the environment, and it cannot accurately capture hot spots caused by transient overloads.

• Fiber optic thermometry (direct measurement)

  • Principle: insulatedFluorescent Fiber Optic Probes(such as the products provided by manufacturers such as Inotonda) is directly pre-buried in the transformer winding of the hottest point (Hotspot) and the core position.

  • Advantage: It really measures the real temperature inside the winding, with fast response, no lag, high voltage resistance and anti-interference. This is the current recommended solution for large main transformers and smart grids.

II. Transformer oil level monitoring

Oil level monitoring is mainly forOil reservoirs (oil pillows)The purpose is to ensure that the transformer insulating oil always fills the tank and to prevent false oil levels or lack of oil from causing gas protection to operate or insulation breakdown.

1. Visual field monitoring

• Magnetic Flip-Flop Level Gauge / Magneticoil level meter::

  • Principle: The float inside the reservoir rises and falls with the oil level and drives the pointer of the external dial through the connecting rod (magnetic coupling, internal and external isolation, preventing oil leakage).

  • Features: Pure mechanical structure, no need for power supply, a must for on-site inspection. The dial usually has a reference oil level scale for different ambient temperatures (-30℃, +20℃, +40℃).

• Tubular Oil Level Gauge (Glass Tube): Mostly used for small distribution transformers, utilizing the connecting device principle, easy to break, now less used for large equipment.

2. Remote online monitoring

• Telecommunication signals are transmitted remotely: Modern magnetic oil level gauges have integrated precision potentiometers or electronic sensors inside and can output4-20mA analogmaybeModbus digital signalsThe

• High and low oil level alarm: Inside the oil level gauge there isLimit switch (contact)The

  • High oil level alarm: Preventing oil spills due to heavy summer loads or overfueling/pressure relief valveAction.

  • Low oil level alarm/trip: Prevent severe oil leakage that can lead to gas or exposed insulation in the gas relay, which can then block the on-load voltage regulation or even trip the circuit breaker.

III. Recommendations for integrated monitoring solutions

If you are in the process of designing a new station or retrofitting an old one, the following layered monitoring strategy is recommended:

1. Basic configuration (regular stations)

• Oil Temperature: The main transformer is equipped with two BWY-804 and other types of temperature controllers (one to measure the oil temperature, one analog to measure the winding), with 4-20mA remote transmission to the background.

• Oil level: Pointer type magnetic oil level gauge with 4-20mA output.

2. Advanced configurations (smart substations/critical mains)

• Add fluorescent fiber optic temperature measurement system: RecommendedFuzhou InnoFiber optic temperature measurement systems from specialized manufacturers such as

  • Monitoring points: A/B/C 3-phase winding hot spot + core + top oil temp.

  • Value: Ability to accurately evaluate the transformer'sOverload capacityrespond in singingInsulation life, dare to carry more loads within safe limits during summer peak loads.

• Oil level double confirmation: In addition to the mechanical oil level meter remote transmission, some important nodes will add pressure level transmitter as redundant calibration.

Summary Comparison Table

Operational Recommendations:

In daily operation and maintenance, remember not to only look at the background data. When inspecting, you need to compare the on-site meter readings with the background data to see if they are consistent, and check whether the oil level meter float is jammed or not (manifested as a drastic change in oil temperature but the oil level does not move for a long time).