Power Industry Applications

 

Power Transformers

Online Monitoring of Moisture in Power Transformers

Moisture reduces the insulating properties of transformer oil and quickens the ageing of the transformer. Traditionally oil moisture readings have been checked at periodic intervals. However, moisture levels can change rapidly rendering periodic sampling methods insufficient. To protect the transformer, timely and cost-efficient maintenance needs to be ensured with a permanently online monitoring system.

The Vaisala HUMICAP® Moisture and Temperature Transmitter Series for Oil, MMT330, accurately measures online the moisture in transformer oil, giving a real-time picture of the oil's condition, an indicator of how well the transformer is operating. The transmitter monitors the moisture levels at all ambient and operating conditions and is compatible with any insulating oil. The measurement can be connected to the substation data-collection system directly. For temporary spot-checks we recommend the lightweight Vaisala

HUMICAP® Hand-held Moisture Meter for Oil MM70.
The long-term stability is ensured by the Vaisala-designed HUMICAP® sensor, the first sensor ever to measure moisture in oil online. Today, Vaisala has 15 years of experience monitoring transformer oil moisture in thousands of transformers world-wide. Industry-leading customers in over 30 countries use Vaisala's equipment to monitor moisture in transformers online.

Measuring the Dew point during Insulation Drying
When building a new transformer or overhauling an installed transformer the cellulose insulation is dried by applying heat and a vacuum to remove water. After the drying procedure the tank is purged with dry nitrogen. Measuring the dew point is a widely used method of monitoring the drying process and confirming the final dryness after the nitrogen purge.

Vaisala offers both fixed and portable dew point instruments that offer fast response time enabling quick and reliable verification that acceptable moisture levels have been achieved.

 

SF6 Gas Insulated Equipment

Monitor Quality of SF6 with Online Dew Point and Pressure Measurement

The electric power industry uses SF6 to insulate switchgears, circuit breakers and other equipment used in electricity transmission and distribution. To ensure the integrity of SF6 gas as an insulator, the amount of water vapor in SF6 gas should be kept to a minimum. Moisture may also increase the formation of unwanted secondary decomposition products, which can lead to arcing and equipment failure.

Online monitoring of SF6 is convenient with Vaisala's Multiparameter Transmitter DPT145. The DPT145 is a unique innovation that not only monitors dewpoint online but also pressure and temperature. In addition the instrument calculates four other values, including gas density and ppm. The DPT145 provides an excellent assessment of the SF6 insulation. Both sudden and minor leaks are detected by the direct normalized pressure measurement, while online dew point measurement alerts the user to moisture issues, which can weaken the insulation properties of SF6 and cause rapid deterioration. Integrating the DPT145 into a condition based monitoring system minimizes the need for on-site visits and helps to ensure that no SF6 is released into the atmosphere.

Spot-checking is easy with Vaisala's hand-held dew point meter DM70 which is a lightweight, battery-powered instrument for measuring the dew point in SF6. It provides fast response time and internal datalogging to optimize the field technician's time. A unique sample cell allows dew point measurement at both in gas pressure and in ambient atmospheric pressure. The cell meets and even exceeds environmental regulations by ensuring protection against accidental discharge of SF6, requiring minimal amount of SF6 for sampling, and enabling collection and recycling of SF6.

 

Turbine Inlet Air

Monitoring Humidity to Optimize Gas Turbine Performance
The accurate measurement of the humidity of inlet air is essential for good turbine control. When the air is cooler the turbine performs better because as the temperature decreases, the density of the air increases. This results in a greater mass of air flowing through the turbine, resulting in increased power generation.
A 1ºC increase in temperature may mean a 0.5% electricity loss. However, inlet air that is too cold or humid must be avoided as it may lead to water condensation or even icing, which damages the turbine blades.

With reliable humidity monitoring the utility operator can cool and compress the inlet air, maximising the power generated without risking condensation.

Vaisala's 30 years of experience of industrial humidity measurements is incorporated into the Vaisala HUMICAP® Humidity and Temperature transmitter Series HMT330. For operators in the power industry this means reliable, stable and accurate measurements. With the HMT330 series you have many versatile options to choose from: a numerical and graphical display, a multilingual menu, alarms, trends, a one-year history, and WLAN/LAN.

 

Hydrogen Cooled Generators

Monitoring the Humidity and Temperature of Hydrogen Cooled Generators to Achieve the Best Yield

Dry hydrogen is used to cool electric generators because of its high thermal conductivity and low viscosity. An increase in the level of moisture in the hydrogen may lead to a decrease in cooling efficiency, a reduction in insulation capability and corrosion of generator parts with the worst outcome being a total breakdown of the generator.

Vaisala’s intrinsically safe HMT360 humidity and temperature transmitter series is ideal for monitoring dryer performance. The sensor can be installed directly into a pressurised pipeline and provides measurements that show if dry hydrogen is being fed into the generator.


Click here for Application Notes

For Power Industry Applications, our products are applicable in:

Power Transformers, SF6 Gas Insulated Equipment, Turbine Inlet Air, Hydrogen Cooled Generators



Products Offered for Power Industry Applications Industry

Vaisala