MO – Online Moisture in Oil Monitor
Excess water in the insulating oil of high voltage equipment, such as transformers and reactors, causes well known adverse effects. High moisture content will cause reduction in dielectric rigidity and migration of water into the insulating paper, with the risk of formation of bubbles and accelerated aging in the presence of high temperatures, thus jeopardizing the equipment life cycle and integrity.
The Moisture in Oil Monitor MO consist of a sensor module, installed in contact with the oil, and an Interface Module that allows on line measuring and monitoring of the moisture present in the oil, generating important information in determining the equipment’s current state:
• Water in oil saturation percentage (RS %) and oil temperature;
• Calculation of water saturation percentage converted to a reference temperature selected by the user (RS% @ TREF), allowing users to know, for instance, what would be the value for moisture saturation for the oil at a reference temperature or at the transformer’s lowest expected operating temperature;
•Calculation of water saturation percentage converted to a second value for temperature, measured by a Pt100Wat 0ºC input sensor (RS% @ T2), allowing users to know, for instance, the level of water saturation if the transformer is de-energized and allowed to cool to ambient temperature (measured with a Pt100 RTD);
• Water content in oil in parts per million (ppm), calculated based on the readings for moisture saturation percentage and oil temperature with user programmable water solubility constants, allowing users to adjust the constants in accordance with the type and age of the oil;
• Evolution trend (rise or drop) in the water content in the oil in ppm per day (ppm/24h).
Based on the above information, the MO’s alarm values are programmed by the user for high or very high moisture saturation percentages (RS%, RS% @ TREF and RS% @ T2), high or very high water content (ppm) and high water content evolution trend.
Main Features:
• IED (Intelligent Electronic Device) designed specifically for substation yard conditions (interference, extreme temperatures), suitable for integration into supervision or monitoring system through RS485 port (Modbus or DNP3.0);
• Easy visualization LED display;
• Programmable analog output for remote reading of RS%, RS% @ T2, RS% @ TREF or water content (ppm). User programmable output range: 0…1, 0…5, 0…10, 0…20 or 4…20mA;
• Six user programmable output relays for alarm indications;
• Internal clock with date and time and non-volatile memory for saving readings;
• Self-diagnosis for internal fault detection. Total absence of mechanical parts in parameter definition and calibration.
• Optional mass memory for recording of measurements and alarms in non-volatile memory.Non-volatile memory type FIFO (First In First Out) with capacity for storage of 1489 registers. Each register includes relative saturation, water content in oil, oil temperature, temperature of sensor 2 (if used), evolution trend of water content and alarm events, based on internal clock with day, month, year, hour, minute and second. A memory recording can be started by:
– User defined time interval between recordings (1 to 1000 minutes), or;
– Variation of water content or oil temperature higher than the dead band selected by users, or;
– Occurrence of any alarm.
Cubicles
The Interface Module of the Moisture in Oil Monitor MO must be installed protected from the weather, and for this reason, it is usually installed inside the transformer’s control panel. For those cases where this is not convenient, such as for example in refitting older transformers, the Interface Module can be supplied in easy-to-install weatherproof cubicles.
Ambient Temperature Sensor
The Moisture Monitor – MO has a second input for temperature sensor, whose reading can be used in calculating the percentage of moisture saturation in oil at this second temperature. Typically this input is used in measuring ambient temperature, which allows monitoring of moisture saturation in oil if the transformer is de- energized.
Ambient temperature is measured by way of Pt100Wat 0ºC type temperature sensor installed in thermal shelter, minimizing errors caused by sun, rain, wind, etc. on the readings. If required, Treetech has available sensors and thermal shelters suited for this type of reading, supplied as optional accessories.