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QLD-120P – Instrument Transformer Comprehensive Tester
The QLD-120P is an all-in-one testing solution for various instrument transformers. It combines comprehensive functionality with a user-friendly interface, providing highly accurate analysis for both current transformers (CT) and potential transformers (PT). With its portable design and one-button operation, the QLD-120P streamlines complex testing procedures in the field and the lab.
Key Technical Features of the Instrument
★ Comprehensive Functionality: Meets the testing requirements of various current transformers (CTs) (e.g., protection, metering, and TP types) for excitation characteristics (i.e., volt-ampere characteristics), turns ratio, polarity, secondary winding resistance, secondary load, ratio difference, and phase angle difference. It can also be used for testing the excitation characteristics, turns ratio, polarity, and secondary winding resistance of various PT electromagnetic units.
★ Automatically provides parameters such as inflection point voltage/current, 10% (5%) error curve, accuracy limit factor (ALF), instrument safety factor (FS), secondary time constant (Ts), remanence coefficient (Kr), and saturation inductance.
★ Tests meet various current transformer standards such as GB1208 (IEC60044-1), GB16847 (IEC60044-6), and GB1207, automatically selecting the appropriate standard based on the transformer type and level.
★ Based on advanced low-frequency testing principles, it can handle CT testing with inflection points up to 80KV.
★ The instrument adopts the internationally popular square wave method, resulting in a more perfect excitation curve.
★ The instrument can store 3000 sets of test data, which will not be lost in the event of a power failure.
★ Testing is convenient and straightforward; a one-button operation completes CT DC resistance, excitation, turns ratio, and polarity tests. Moreover, except for load testing, all other CT tests use the same wiring method.
★ Easy to carry, the instrument weighs approximately 7 kg.
Main technical parameters of the instrument
| Technical Parameters | Specifications |
|---|---|
| Input Power Voltage | AC100264V; 5060Hz |
| Output | 0~180Vrms, 12Arms, 36A (peak) |
| Voltage Measurement Accuracy | Range: 2~100Vrms, Accuracy: ±0.1% |
| CT Ratio Measurement | Range: 1~40000, Accuracy: ±0.1% |
| PT Ratio Measurement | Range: 1~40000, Accuracy: ±0.1% |
| Phase Measurement | Accuracy: ±2min, Resolution: 0.5min |
| Winding Resistance Measurement | Range: 0~300Ω, Accuracy: 0.2% ± 2mΩ |
| AC Load Measurement | Range: 0~1000VA, Accuracy: 1% ± 0.2VA |
| Current Boost Function (Optional) | Range: 0150A; Time: 0180S |
| Operating Environment | Temperature: -20°C~50°C, Humidity: ≤90% |
| Dimensions & Weight | Dimensions: 340mm × 260mm × 140mm, Weight: ≈7kg |
Current Transformer (CT) Testing
3.1 Test Wiring
Step 1: For CT, when performing resistance, excitation, or ratio tests, connect the wires as shown in Figure 3.1; when performing load tests, connect the wires as shown in Figure 3.2.
- Note 1: In the wiring diagram of Figure 3.1, for the transformer bushing CT, its primary sides P1 and P2 can be connected to both ends of the transformer winding where the CT under test is located.
- Note 2: In the wiring diagram of Figure 3.1, for the CT on the GIS (SF6) switch, all switches connected to the primary busbar must be disconnected, and the grounding switch must be closed. At this time, the primary side P2 is grounded, and P1 is connected to the primary busbar. It should be ensured that P1 and P2 are not open circuits.
Step 2: Open all other windings of the same CT, ground one end of the primary side of the CT, and also ground the equipment.
Step 3: Turn on the power and prepare for parameter settings.
3.2 Parameter Settings
Step 1: Select the main interface menu option to open the CT test parameter settings interface.
Step 2: Enter the appropriate number and winding to ensure a suitable report name when saving the report after the test.
Step 3: Click on the test item and select the corresponding test item from the drop-down menu.
Step 4: Enter Current Temperature: The winding temperature during testing. Generally, the ambient air temperature at the time of testing can be entered.
Step 5: Enter Secondary Current: This is the CT’s secondary current rating, typically 1A or 5A.
Step 6: Select Rated Frequency: This refers to the CT’s rated operating frequency. Selectable values are 50Hz or 60Hz.
Step 7: Select Winding Level: For CTs, there are four options: P (Protection), TPY (Transient Protection), M (Metering), and Zero (Zero Sequence). Different options result in different subsequent parameters.
Step 8: Enter Maximum Current: Generally, set it to the rated secondary current. For a CT with a rated secondary current of 5A, set it to 5A; for a CT with a rated secondary current of 1A, it can generally be set to 1A.
Step 9: Enter Primary Current: The CT’s rated primary current, used to calculate the accurate actual current ratio.
Step 10: Input Sn/cos Ф: Sn refers to the rated load on the nameplate, and cos Ф refers to the power factor, which is usually 0.8 or 1.
Step 11: For P-level, metrology-based, and TPY-level CT scans, the parameter-setting interfaces are shown in the images above. Their respective special parameter settings are shown in the table below.
| Parameter | Description | P | TPY | Unit |
|---|---|---|---|---|
| ALF | Rated Accuracy Limit Factor, specified on the nameplate. For example, 5P20 means ALF = 20; 10P15 means ALF = 15. | √ | ||
| Kssc | Rated Symmetrical Short-Circuit Current Factor, specified on the nameplate. Default: 10. Used to calculate the limiting EMF and its corresponding peak transient error. | √ | ||
| Tp | Primary Time Constant. Default: 100ms. | √ | ms | |
| Ts | Secondary Time Constant. Default: 3000ms. | √ | ms | |
| Operating Cycle | C-t1-O or C-t1-O-tfr-C-t2-O. Default: C-t1-O cycle. | √ | ||
| t1 | First Current Flow Duration. Default: 100ms. | √ | ms | |
| tal1 | Primary Current Flow Accuracy Limit Duration. Default: 40ms. | ms | ||
| tfr | Delay between First Opening and Reclosing. Default: 500ms. Displayed only when the C-t1-O-tfr-C-t2-O cycle is selected. | √ | ms | |
| t2 | Second Current Flow Duration. Default: 100ms. Displayed only when the C-t1-O-tfr-C-t2-O cycle is selected. | √ | ms | |
| tal2 | Secondary Current Flow Accuracy Limit Duration. Default: 40ms. Displayed only when the C-t1-O-tfr-C-t2-O cycle is selected. | √ | ms | |
| Fs | Rated Instrument Security Factor, specified on the nameplate. Default: 10. | √ |
Step 12: Select the Start button on the right to start the experiment.
Safety Precautions
1. To protect the equipment and your personal safety, please read the instruction manual carefully before use and operate strictly according to the instructions.
2. Do not place this instrument on an unstable platform or table to prevent damage from falls.
3. The fan and ventilation holes on the side of the instrument are for ventilation and heat dissipation. To ensure the instrument’s regular operation, please do not block them.
4. This instrument is a precision electronic instrument. When using it outdoors, please avoid exposure to direct sunlight and high temperatures. Ensure adequate shade and ventilation to prevent overheating or decreased measurement accuracy.
5. As a safety measure, this instrument is equipped with a protective grounding terminal. Before testing, ensure the grounding terminal on the instrument’s side is reliably grounded.
6. The instrument operates on 100~264V (50/60Hz) AC power. Use a power cord rated at 10A or higher.
7. Do not allow any foreign objects to fall into the casing to avoid short circuits.
8. During transportation, please place cushioning materials such as sponge around the instrument to prevent damage or reduced accuracy due to vibration and bumps.
9. Do not arbitrarily delete historical test records saved on the central unit to avoid data loss.
