Question

Please use at least 200 words to describe the following questions:

Evaluate the calibration of the PDT and ultrasonic sensor system by discussing the significance of: The maximum linear error in distance and the percent full-scale error.

Answer 1

Calibration of the PDT and ultrasonic sensor system:

Insulation material for electric apparatus used in high voltage and strong electric field condition will deteriorate progressively, because of discharge, electromagnetic force, thermal stress, and so on. So partial discharge will appear at strong electric field locations, and it’s the symptom of insulation defects. Ultrasonic partial discharge detector can discover and locate the partial discharge using the ultrasonic sensor receiving the ultrasonic signals produced by partial discharge in GIS or transformer. Ultrasonic partial discharge detector can detect wide frequency range, from 20 kHz to 200 kHz. Besides, ultrasonic method is unauthoritativeness, so it has better capacity of resisting disturbance and higher sensitivity. Because of the above excellence, ultrasonic partial discharge detector is widely used to detect partial discharge in GIS and transformer in power system and obtain good results. With the development of science and technology and the progress of society, more and more ultrasonic sensor and partial discharge detector were produced by different producer. There are so many styles and kinds that detector functions are intermingled. For example, center frequency, frequency range, sensitivity are different widely, making the detect results are highly varied. So it is necessary strongly to standard and start the calibration technology and application of ultrasonic partial discharge detector. The paper introduces the method and application for ultrasonic partial discharge detector calibration. Detector theory of ultrasonic partial discharge detector When partial discharge appearing, numerator will strike each other strongly, and insulation gets bigger in a moment because of heat. All the elements will appear impulse of pressure wave in macroscopic phenomenon, ultrasonic wave is one of frequencies are bigger than 20 kHz. At the
moment of partial discharge, the location of discharge can be seen a pulse signal spot, sound wave will disseminate all around in the shape of spherical wave, conforming to the laws of mechanical wave propagation. It disseminates with different speed at different medium and generates reflex and refraction at medium boundary. Ultrasonic sensors installed at external part of equipment can detect partial discharge signals by changing ultrasonic signals to electric signals, filtering, amplifying and so on. System structure of ultrasonic partial discharge detector is shown in Fig. 1. It is made up by ultrasonic sensor, preamplifier, filter, post-detector, digital processing oscilloscope, the final signals can be seen in the computer directly.
Fig. 1 system structure of ultrasonic partial discharge detector Company standard of State Grid “Technical Regulations of Ultrasonic Partial Discharge Detector” wasformulated recently. It formulatesthe technicalregulations of ultrasonic partial discharge detector.
(1) Sensitivity of ultrasonic sensor: Sensitivity is the response to ultrasonic signals. It’s one of the important performance criteria, and can be shown in V/(m/s). Technical Regulations demands: peak sensitivity of ultrasonic sensor is higher than 60 dB( V/(m/s)) and average sensitivity is higher than 40dB( V/(m/s)).
(2) linearity error: is less than ±20%.

PDT:

For any laboratory work, calibration is necessary to ensure accurate measurements. Calibration is the process of comparing a known input measurement to the given output measurement on a specific device. For the purpose of this lab, a potentiometric displacement transducer will be calibrated using known input measurements from different sources. A potentiometric displacement transducer takes an input distance in which the piston is pulled out and in turn outputs a corresponding voltage. In this lab, the measurements taken of the output will allow theuser to calculate the sensitivity and other characteristics of the instrument. When the calibration of an instrument is off, an entire experiment can be thrown off. The relationship between the voltage and displacement of the transducer, in this case, must be determined in order to preventsuch errors. For this lab, the calibration and performance characteristics should be found by the user and evaluated in terms of the caliper. This lab and calibration in any scientific context is important and necessary because it is the base of all quantitative findings. Any experiment usinginstruments to measure values or outputs needs to calibrate said instruments before beginning the experiment or all findings could be unusable. Measuring tools in the lab are not usable

without proper calibration, for this experiment, the performance characteristics of a PDT need tobe determined, as well as the device needs to be calibrated in order to be ready for use in a lab setting. MethodThis experiment uses two different types of calipers, Vernier caliper and dial caliper, to compare the range and resolution of the PDT along with other measurement characteristics. In order to obtain data from the experiment comparing the input and output of the PDT, the PDT is connected to a battery and a voltmeter to control the voltage. In the experiment comparing the displacements measured by the calipers and PDT, the calipers are simply added in to measure the displacement of the voltmeter.