In combination with UHF sensor, acoustic and electric combined sensor, ultrasonic sensor and broad-band current transformer, HCL2012 partial discharge tester can be used to detect partial discharge of high-voltage equipment on-line such as power transformer, high voltage switchgear, GIS and cable joints. It is characterized by carry-everywhere convenience, fast measurement, strong anti-interference.
The configured software has functions like real-time waveform diagram, peak display, locating etc and can also perform a detailed analysis of certain phase waveform. You can make a window larger or smaller at random and also carry out an analysis of data spectrum. A comprehensive and statistical analysis of test data minimizes the effect of non-stable factors on test results.
Test data and transient discharge waveforms can be stored automatically or manually for future reference.
Technical Parameters :
1. Number of channels: 2/4 electric signal interfaces & 1 EXT interface
2. Sampling frequency: maximum 200MGa/s
3. Sampling precision: 12bit
4. Range: 0.1mV~20V
5. Range switch: 1mV, 2mV, 5mV, 10mV, 20mV, 50mV, 100mV, 200mV, 500mV, 1V, 2V, 5V
6. Frequency band range: 1Hz-60MHz
7. Range non-linear error: 5%
8. Range of capacitance for test object: 6pF~250µF
9. Power source mode: internal lithium cell / AC 220V
10. Display: 6.5 inches TFT LCD
11. Resolution: 640×480
12. PV: 4GB
13. Hard disk: 32G stiff disk used for storing the test data
14. RS232*1 interface: used for synchronous transmission with PC
15. USB*2 interface: can be externally connected with mouse, keyboard and movable storage equipment
16. Interface power source mode: battery (16.8V lithium cell ) + External power source (220V AC)
17. Electric signal interface: 2/4 BNC interface used for inputting the signals
18. BNC interface: EXT interface
19. USB*1: used for connecting the network
20. Grounding button: external grounding
21. CPU: main frequency 1.6GHz
22. System: WIN7
23. Temperature: -20℃ - 60℃
24. Relative humidity: -20℃ - 45℃
25. Dimension: 280mm * 190mm * 80mm
26. Weight: 3kg
27. Host: used for acquiring the signals; displaying the waveform; storing and processing the data
28. Ultrasonic sensor: used for measuring ultrasonic signals from PD
29. Ultra-high frequency sensor (UHFS): used for monitoring ultra-high frequency signals caused by GIS partial discharge
30. High frequency current transformer (HFCT): used for measuring PD signals which pass through grounding lines of equipment
31. Combination detector: used for measuring partial discharge of HV equipment including cables and dry transformer.
Ultra High Frequency Partial Discharge Tester for Transformer:
1.Principle of ultrasonic method
When the discharge signal generates inside the power transformer, besides generating discharge pulse current transmitting along the capacitive circuit, it will also stimulate mechanical wave (ultrasonic) signals, which emit in all directions through the transformer. Although the structure of power transformer is complex, the whole body of transformer is filled with transformer oil, and parts including windings, insulating materials, supports, clamps, wires are immersed in oil. The transformer oil acts as a good medium for ultrasonic transmission, which is good for detecting the ultrasonic signals. Therefore, an ultrasonic sensor is placed outside the oil tank to receive larger internal discharge signals.
2.Principle of pulse current method
Due to the structure of power transformer, there are hundreds or even thousands of distributed capacitance between windings and iron core, and up to hundreds pF between windings and oil tank. When the partial discharge occurs in the circuit of main insulation, generated HF signals cover from tens of Hz to tens of MHz even to GHz. The discharge signals will transmit through all circuits which are in capacitive relation to discharge point, among of which there must be core grounding circuit. Hence, installation of one high frequency current transformer on the core earthing wire can effectively receive discharge signals of the transformer.
Ultra High Frequency Partial Discharge Tester for Switch Cabinet:
1.Principle of ultrasonic method for switch cabinet
The phenomenon of partial discharge has various characteristics. When discharging, it not only emits electromagnetic signals, but also produces acoustic emissions. Partial energy of PD will transmit to surroundings in the form of acoustic waves. The ultrasonic sensors can be used to detect these acoustic pulses, thus reflecting the status of partial discharge. The method of testing the characteristics of acoustic waves in the partial discharge signal is called the ultrasonic method. Acoustic waves are generated during the discharge of the switch cabinet. The spectrum of acoustic waves generated by the discharge is broad, ranging from tens of hertz to tens of megahertz. Among them, the signals, the frequency of which is below 20kHz, can be heard by the human ear while others above this frequency must be received by the ultrasonic sensor.
2.Principle of earth electric wave method (special for switchgear)
When the partial discharge occurs to the ground insulating part of switch cabinet, there will be small quantity of capacitive discharge between HV conductor and earthing metal shell. This kind of discharge is characterized by small quantity and short duration (a few nanoseconds). Because the discharge point is within the switchgear, the voltage pulse generated by the electromagnetic wave transmits on the inner surface of the metal shell and is shielded by the metal shell. If shielding layers are continuous, the discharge signal can not be detected outside. In fact, shielding layers are usually not continuous due to their locations. When the voltage pulses pass through these discontinuities, they will transmit through these channels and then to the ground along the metal shell. At the same time, a transient earth voltage generates in the metal cabinet (usually in the tens of millivolts to several volts, and keep for only a few nanoseconds). The capacitive sensor can be put on the metal box of running switch cabinet to detect the signal.
The transient earth voltage (TEV) method mainly detects busbar (joints, bushings and supporting insulators etc), circuit breaker, CT, PT and cable joints. These parts are mostly located in the middle and lower sections of switch cabinet front panel, upper, middle and lower sections of back panel, the upper, middle and lower sections of side panel (See Fig.5 ).
Ultra High Frequency Partial Discharge Tester for Cable and Accessories:
1.Principle of acoustic & electric combined detector detection
When the partial discharge occurs to cables, ultrasonic waves and electromagnetic generate and emit in all directions focusing on the fault point. The electromagnetic wave transmits much faster than the ultrasonic wave. If measuring at a certain distance from fault point, there is time difference between electromagnetic signal and ultrasonic signal. The discharge position is calculated according to the time difference. Based on this principle, the combined detector measures electromagnetic signal and ultrasonic signal at the same time. The fault point location is calculated according to the signal time difference.
2. Principle of pulse current method
In the cable, the conductor and metal shielding are separated by insulating material forming distributed capacitance up to hundreds of pF. For high frequency signal, it is a good conductor. Therefore, the broad-band current transformer can be installed on the shielding earthing wire of the cable joint to detect discharge pulse signals and determine the value of partial discharge.
Ultra High Frequency Partial Discharge Tester for GIS :
1. Principle of UHF detection
The lower frequency limit of UHF detection is more than 300MHz, and the upper limit is 1000MHz and above. Therefore, the interference caused by corona discharge, is eliminated and its anti-interference performance is the best. The UHF method is to tightly attach the concave surface of UHF sensor (ultra-high frequency sensor) to the GIS basin-type insulator. Some GIS basin insulators have shielding layers with measurement window. The UHF sensor can be aligned to the measurement window, and the GIS internal discharge signal can be taken out.
2. Principle of ultrasonic detection
The ultrasonic method is to place the sensor outside the GIS, and the sensitivity of the sensor ranges from 20KHz to 100KHz. Using this method can detect, identify and locate the faults in the GIS without the need to install the internal coupler and sensor on the GIS in advance. Increasing frequency can reduce the impact of environmental noise, and the sensitivity of this method is high for most common faults. For the moving particles, this method is better than traditional methods, UHF and VHF method. There are still some problems in detecting the discharge caused by particles on insulator. Because the attenuation of ultrasonic signal in epoxy insulation is very large, this method can not be used to measure defects in epoxy resin insulation, such as bubbles.
HIMALAYAL provides innovative products that comprise high voltage test equipment, full-set high voltage test instruments, on-site test systems and on-line monitoring systems, and services regarding tests, diagnostics and asset monitoring for clients in power industry. We help to ensure safety and reliability in the power generation, transmission and distribution.