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Window Media |
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Low (2,793 meg) |
High (16,212 meg) |
Low (3,528 meg) |
High (13,903 meg) |
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Partial discharge is an electrical discharge or spark that bridges a portion of the insulation between two conducting electrodes. Partial discharge can occur at any location within the insulation system (between the two electrodes) where the electric field strength exceeds the breakdown strength of that portion of the insulating material. Partial discharge can occur in voids within solid insulation, across the surface of insulating material due to contaminants or irregularities, within gas bubbles in liquid insulation or around an electrode in gas (corona activity).
Partial discharge may occur in aged, defective or poor quality insulation and can propagate and develop until the insulation is unable to withstand the electrical stress leading to flashover and failure. When partial discharge activity occurs, it emits energy in the following ways:
- Electromagnetic:
- Acoustic:
- Gases:
Non-intrusively, the most practical methods of locating partial discharge activity involve the detection of Transient Earth Voltages (TEV) in the radio frequency part of the electromagnetic spectrum and airborne ultrasonic emissions.
These techniques are complimentary and their application enables a comprehensive assessment of the condition of insulation on medium voltage switchgear to be non-intrusively assessed.
Partial discharge activity accounts for the largest percentage of disruptive failures of medium voltage switchgear. Therefore, the early detection of partial discharge activity provides an early warning of problems and can prevent failure of equipment.
EA Technology manufactures a range of partial discharge test equipment that can non-intrusively detect and measure partial discharge activity using both Transient Earth Voltage and ultrasonic techniques.
The UltraTEV® Detector
The UltraTEV Detector is the worlds first lightweight hand held instrument that can detect both Surface Discharges using ultrasonic sensors and internal TEV Discharges using electro-magnetic sensors. Designed for use by engineering and non-technical staff, the UltraTEV Detector combines the ability to detect and indicate the strength of transient earth voltages (TEV) produced by defective insulation, as well as indicate the presence of destructive surface discharges.
UltraTEV® Calibration Checker
The easy-to-use accessory enables operators to confirm that their UltraTEV Detectors™ are correctly calibrated, without the cost and inconvenience of returning them to the company each year to be tested. Units only need to be returned if they are outside their specified calibration. The Calibration checker only requires an annual calibration to ensure it is functioning correctly.
The MiniTEV
The MiniTEV is a compact self contained hand held unit that detects partial discharge magnitude using the TEV technique. The instrument also has the ability to count the number of discharge pulses detected during a 2 second measurement period and this can be used to further gauge the severity of any detected partial discharge activity.
 Locator
The magnitude of the transient earth voltage signal is measured using this instrument in single probe mode. Using the instrument in two probe mode allows the location of the discharge site to be determined. These measurements are invaluable in determining the current condition of substation equipment, allowing maintenance to be targeted more effectively and economically.
Monitor.
Partial discharge activity may be intermittent in nature. The discharge site may lie dormant for hours on end and then be initiated by a voltage surge or by changes in temperature or humidity. The PDM03CF is designed to not only detect the presence and magnitude of partial discharges 24 hours per day, but using an array of precedence detector circuits, indicate the location of these discharges.
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