Original title: Annual inspection and testing instrument for cables after commissioning

Annual inspection and testing instrument for cables after commissioning

First test of new winding

The pilot testing equipment adopts a dedicated voltage withstand tester, and the selection of the instrument should be based on the specifications of the measured motor. The testing method, peak value, and related precautions include:

The high voltage output end of the step-up transformer is connected to the tested winding, and the low voltage end is grounded. The grounding wire at the testing site must be checked regularly

The tested motor casing (or iron core) and the winding without high voltage should be reliably grounded.

The test pressurization time is divided into two types: 1 minute and 1 second; For finished motor products, a 1-minute withstand voltage test shall be conducted, and the voltage value shall be in accordance with the specific provisions of GB755.

After the cable is put into operation, the annual inspection and testing instrument for the semi-finished products of motor stator and winding motor rotor should be increased compared to the whole machine, as specified in the technical conditions.

35kV cable frequency conversion series resonance 5km

1. Introduction

ZSBX-35kV cable frequency conversion series resonance 5km

1. Assist in implementing preventive AC withstand voltage tests and handover AC withstand voltage tests for various test subjects;

2. Test the insulation ability and capacitive load of cross-linked rubber power cables, power transformers, GIS, transformers, insulators, generators, switches and other test objects to withstand various overvoltages

Communication withstand voltage test.

2. Technical parameters

Test object: AC withstand voltage test of 5km 35kV/400mm2 cable, capacitance ≤ 1.073uF, test frequency 30-300Hz, test voltage 52kV, test time 60min

Rated capacity: 810kVA;

Input power supply: three-phase 380V voltage, frequency 50Hz;

Rated voltage: 54kV;

Rated current: 15A;

Working frequency: 30-300Hz;

Device output waveform: sine wave

Waveform distortion rate: Output voltage waveform distortion rate ≤ 1%;

Working time: Continuous 60 minutes allowed under rated load; Overvoltage 1.1 times for 1 minute;

Temperature rise: After continuous operation for 60 minutes under rated load, the temperature rise is ≤ 65K;

Quality factor: The device itself has a Q ≥ 30 (f=45Hz);

Protection function: It has overcurrent, overvoltage, and flashover protection for the test sample (see the variable frequency power supply section);

Measurement accuracy: System effective value of 1.5 level;

Pilot test holding incentive transformer ZSJLB-45kVA/3kV/0.4kV 1 unit

Rated capacity: 45kVA;

Input voltage: 0-400V, single-phase;

Output voltage: 3kV;

Working time: 60 minutes;

Structure: Oil type;

Weight: Approximately 350kg;

Size: 700 * 600 * 400

Variable frequency power supply ZSXB-F-45kW/380V 1 set

Rated output capacity: 45k

Working power supply: 380 ± 10% V (three-phase), power frequency

Output voltage: 0-400V, single-phase,

Rated input current: 112.5A

Rated output current: 112.5A

Voltage resolution: 0.01kV

Voltage measurement accuracy: 1.5%

Frequency adjustment range: 30-300Hz

Frequency adjustment resolution: ≤ 0.1Hz

Frequency stability: 0.1%

Running time: 60 minutes continuously at rated capacity

Continuous operation for 60 minutes at rated capacity, component high temperature ≤ 65K;

Noise level: ≤ 50dB

High voltage reactor ZSDK-405kVA/54kV, 2 sections, controlled by pilot plant

Rated capacity: 405kVA;

Rated voltage: 54kV;

Rated current: 7.5A;

Inductance: 35H/single section;

Quality factor: Q ≥ 30 (f=45Hz);

Working time: 60 minutes;

Structure: Oil type;

Weight: Approximately 750kg;

Size: Φ 650 * 900mm

One set of ZSFR-60kV/1000pF capacitor voltage divider for pilot holding

Rated voltage: 60kV;

High voltage capacity: 1000pF

Dielectric loss: Tg σ ≤ 0.5%;

Voltage division ratio: 1000:1

Measurement accuracy: effective value of 1.5 level;

Working time: 60 minutes;

Weight: approximately 12kg;

Size: Φ 160 * 850mm

Compensation capacitor voltage divider ZSFRC-60kV/10000pF 1 set

Rated voltage: 60kV;

High voltage capacity: 10000pF;

Working time: 5 minutes;

Weight: 12kg;

Size: Φ 150 * 600mm;

5KV (35/0.4KV) dry-type transformer

(1) Transformer parameters

1. Rated capacity: 2500KVA

2. Rated voltage: 35/0.4KV

3. Rated current: 41.2/3608A

4. No load current%: 1.4%

(2) Calculate the applied voltage

1. No load current: I=3608 × 1.4%=50.5A

2. Partial discharge test for Y, yno connection transformer

Connect the winding to an ungrounded system:

System high voltage: Um=40.5KV

Partial discharge test pre applied voltage: U1=1.5Um=1.5 × 40.5=61KV

Partial discharge test voltage: U2=1.1UM=1.1 × 40.5=45KV

Transformer ratio: K=35/√ 3/0.4/√ 3=87.5

Apply voltage on the secondary side ao

Secondary voltage at 1.5Um voltage: U=1.5Um × 2/3 ÷ 87.5=464V

Secondary voltage at 1.1Um voltage: U=1.1UM × 2/3 ÷ 87.5=342V

Transformer induction withstand voltage test:

Test voltage is taken as twice the rated voltage: Us==70KV × 0.8=56KV

Secondary voltage: U==56 × 2/3 ÷ 87.5==427V

3. Partial discharge test for D, yn11 wiring transformer

Connect the winding to an ungrounded system:

System high voltage: Um=40.5KV

Partial discharge test pre applied voltage: U1=1.5Um=1.5 × 40.5=61KV

Partial discharge test voltage: U2=1.1UM=1.1 × 40.5=45KV

Transformer ratio: K=35/0.231=152

Secondary voltage at 1.5Um voltage: U=1.5Um ÷ 152=400V

Secondary voltage at 1.1Um voltage: U=1.1UM ÷ 152=290V

Transformer induction withstand voltage test:

Test voltage is taken as twice the rated voltage: Us==70KV × 0.8=56KV

Secondary voltage: U==56 ÷ 152==368.4V

4. Excitation transformer capacity:

S=U×I=464×50.5=23.4KVA

1. AC voltage withstand test power supply processing

After the cable is put into operation, the annual inspection tester for high-voltage cable AC withstand voltage uses a frequency conversion resonance device to generate the test power supply. The frequency conversion cabinet is the core component of the device. The frequency conversion cabinet obtains the required frequency for the test through rectification and inversion of thyristors, and introduces a large amount of high-frequency pulse current components during the power conversion process.

The power output of the frequency conversion resonance system cannot be directly used as the power supply for cable partial discharge testing and applied directly to the test object for partial discharge testing. Effective measures must be taken to preprocess the test power supply by setting series reactance, anti corona wire, and voltage equalization ring to improve the quality of the test power supply

2 Cable Terminal Partial Discharge Test Circuit

The partial discharge test circuit of the cable terminal, when partial discharge occurs inside the tested cable, the coupling capacitor instantly charges the cable terminal, forming a high-frequency pulse charging current waveform. The amplitude and frequency of the pulse current reflect the severity of the partial discharge inside the cable. The two sensors of channel 1 and channel 2 transmit the partial discharge signal to the partial discharge diagnosis system for analysis and processing.

At the middle joint of the cable, as shown in the testing principle, there is a capacitance Ca between the armor of one side of the cable and the cable conductor, and a capacitance Cb between the conductor and the armor of the other side of the cable. If partial discharge occurs at the middle joint of the cable, two capacitors C1 and C2 are formed. At this time, Ca and Cb will charge and discharge to C1 and C2 through the conductor, forming a partial discharge current circuit. A high-frequency and low resistance capacitor arm C0 and a high-frequency current sensor are bridged in the shielding layer of both sides of the cable to detect the pulse current signal of partial discharge

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