NDJS-R Capacitive Equipment Dielectric Loss Live Tester

Product Introduction

         There are typically two monitoring methods for the insulation condition of high-voltage electrical equipment in substations: online monitoring and live (portable) online testing. The online monitoring method can obtain characteristic parameters reflecting insulation abnormalities at any time, facilitating automated management, but it requires relatively high investment, involves complicated installation, and requires regular maintenance. In contrast, portable live testing offers advantages such as lower investment, strong targeting, and ease of installation, maintenance, and updates. By pre-installing sampling units on electrical equipment, periodic testing of operating equipment can be conducted using portable live testing instruments, achieving the goal of timely detection of insulation defects and extending the outage pre-test cycle. This can fully replace the more costly online monitoring method. Both the sampling units and testing instruments in this detection system are far superior to previous systems in terms of technology and usability (previous sampling units had safety issues, and testing instruments were inconvenient to operate and could not be easily upgraded to online monitoring systems).

       The Capacitive Equipment Insulation Online Tester adopts a new design structure that overcomes the aforementioned shortcomings of existing live testing systems and offers multiple testing functions. It can perform online or outage measurements of the dielectric loss and capacitance of capacitive equipment. It is primarily used for real-time online monitoring of parameters such as capacitance, dielectric loss value, and end-screen current of operating transformer bushings, CTs, CVTs, and coupling capacitors to determine the insulation status of the equipment.

Product Features

☆、Uses high-precision external through-core current sensors to replace the previously commonly used "sampling protection unit" (which contained multiple switch circuits and was used to switch the end-screen current to the testing instrument during testing, posing a risk of end-screen open circuit and requiring the operation of multiple shorting tabs to introduce the end-screen current into the testing instrument). This sensor features a through-core structure, installed near the equipment, with no break in the end-screen lead and very short lead distance, fundamentally avoiding safety issues such as end-screen open circuits. The sensor can accurately detect input signals in the range of 100μA to 800mA. It has low input impedance, can withstand 10A power frequency current and 10kA lightning current impact, meeting the conditions for online testing;

☆、The sensor adopts a die-cast aluminum shell with a sealed waterproof design, and the secondary output uses a waterproof cable connector for convenient testing connections. After the sensor is installed, testing only requires connecting the secondary cable, achieving "plug-and-play" without any operation on the end-screen signal leads;

☆、The core processor in the testing instrument uses a real-time embedded operating system and an external 16-bit, high-speed, multi-channel synchronous sampling analog-to-digital converter (A/D) to achieve real-time measurement and high-precision calculation of monitored quantities. It can monitor multiple devices simultaneously; provides two online dielectric loss testing methods: measuring the dielectric loss difference and capacitance ratio of two same-phase capacitive devices, and using the PT secondary voltage as a reference signal to measure the capacitance and dielectric loss value of the equipment. It uses self-compensating high-precision current sensors and advanced digital filtering technology to effectively address the accuracy and stability issues of dielectric loss testing. Combined with comprehensive electromagnetic isolation measures and advanced digital filtering processing technology, it ensures that dielectric loss testing results are unaffected by harmonic and pulse interference;

☆、Added the function of detecting the dielectric loss difference and capacitance ratio of same-phase capacitive devices, which not only avoids distortion of dielectric loss test results caused by using PT secondary voltage as a reference signal but also helps reduce the impact of inter-phase electric field interference;

☆、The tester is equipped with a 7-inch LCD and capacitive touch screen to display monitoring data and present monitored voltage, current, dielectric loss, capacitance ratio, and other data in trend graphs;

☆、The tester not only has the function of online real-time testing but can also perform long-term continuous online monitoring of equipment and automatically record the monitored data;

☆、Provides two resistive current detection methods: using PT secondary voltage or using the leakage current of same-phase capacitive devices, enabling accurate measurement of various parameters such as voltage, current, and dielectric loss;

☆、The system uses external sensors to replace the "sampling protection unit," allowing easy upgrade from "live testing" to "online monitoring" while the equipment is in normal operation. Upgrading does not require removal of installed sensors or equipment outage; only the addition of a monitoring unit (IED) is needed;

☆、The tester adopts a portable design structure, is lightweight, easy to operate, and uses a high-capacity lithium battery inside, fully meeting the requirements for field use.

Technical Parameters

☆、Overall Parameters

      Display: 7-inch high-brightness TFT LCD, especially suitable for outdoor use

      Power Supply: Internal high-capacity lithium-ion battery

       Ambient Temperature: -20 to 60°C

       Cable Accessories: Two 25m measurement cables

       Dimensions: 345mm × 295mm × 175mm

       Weight: 4kg

☆、Measurement Range and Accuracy

       Current Measurement: Range   Cx=100μA to 800mA

                                         Cn=100μA to 800mA

       Accuracy  ±(0.5% of reading + 1 digit)

       Voltage Measurement: Range   Vn=3V to 300V

       Accuracy  ±(0.5% of reading + 1 digit)

       Dielectric Loss: Range   Tanδ= -20% to 20%

      Accuracy   ±0.05%

       Capacitance Ratio: Range   Cx:Cn=1:1000 to 1000:1

       Accuracy  ±(0.5% of reading + 1 digit)

       Capacitance: Range  Cx=10pF to 0.5μF

       Accuracy  ±(0.5% of reading + 2 digits)

       Note: Actual measurement accuracy depends on the magnitude of the test object current and the accuracy of the PT (or CVT) used.

☆、Other Features

      Waveform Display: Can display the waveform of the measured signal in real time for more intuitive analysis.

      Harmonic Suppression: Waveform distortion of the input signal does not affect dielectric loss measurement accuracy.

      Power Management: When the internal battery is low, an audible warning is issued, and the device automatically shuts down.

      Charging Time: Less than 6 hours when powered off.