I.System protection

1.Emergency button

 In order to disconnect the power supply quickly when an emergency is detected during the test, an emergency stop button is provided on the operation panel, and the test circuit can be quickly broken by pressing it for emergency use.

2.Warning Light

The system is equipped with a warning light, in which the warning light is lit up after the test starting to show the reminder;

 The system is equipped with an alarm bell, and the tester can manually or automatically control the system to sound a reminder.

3. Equipment protection

   In order to protect the safety of equipment operation, the system is provided with four levels of protection, input protection, output rotection, measurement protection and test protection to ensure that the test item or test equipment can be promptly alerted and quickly implemented during the test process. After a protection action, the system will give a corresponding prompt to determine the cause of the failure.

3.1 input protection

An over-current relay protection is provided at the input of the voltage regulator, which is set according to the input rated current of the voltage regulator to ensure that the current at the input of the voltage regulator is not excessive, and can be used as backup protection for output protection;

A motor protector is installed on the starting side of the traction motor of the generator set, and is set according to the rated current of the motor to ensure the safe start of the generator set.

3.2 output rotection

Over-current relay protection is provided at the output of the voltage regulator and generator set, and the rated output currents of the voltage regulator and the generator set are set separately to ensure that the current at the output of the voltage regulator is not excessive;

The voltage and current signals are measured at the output of the voltage regulator and the generator set. The voltage and current signals are converted into RS/485 signals by a digital sensor into the PLC, and then the rated voltages amd current at the output terminals of the voltage regulator and the generator set are set within the PLC. This protection is used as backup protection for overcurrent relays.

3.3 measurement protection

The test software is provided with protection for the measuring equipment. In the test process. If the measured voltage or current value exceeds the voltage and current range of the precision measuring transformer or power analyzer, the system will be in a certain safety margin at the first time. A warning is issued and the step-up operation is suspended. If the voltage and current measurement exceeds this safety margin, the system immediately will perform an emergency stop operation immediately, and cut off all loop control components and gives a prompt.

3.4  Zero boost protection

In order to ensure that the system can be boosted and powered up from zero, the system will automatically return the voltage regulator to zero (low limit) after disconnecting the output power. And if the voltage regulator is not in the zero position before power transmission, the regulator should be reduced to zero position, and then the power transmission operation is performed. If the voltage regulator cannot reach the zero position, the system prompts that the power transmission operation cannot be performed.

4. Subject protection

In accordance with the rated voltage and current value of the input terminal of the tested transformer, overvoltage and overcurrent protection are set up. After the protection action, the test software gives the corresponding hints. This protection belongs to the protection set in the computer program. It fails in the test of the small transformer but can not reach the higher level protection. Fixed value can be used as an effective means to protect the tested transformer

5.Other protective measures

 The system can reserve multiple contact points for special purpose (user defined, such as protective door or emergency stop button in test area).

II. Matters needing attention

1. The equipment buyer only needs to provide a three-phase power distribution cabinet with a frequency of 50Hz±0.1 and a current of not less than 500A;

2 The grounding resistance of the installation site shall not be greater than 0.5 ohm; in order to maintain the integrity of the site, it is best to pre-dig the cable trenches in the control room and equipment area during civil construction;

3. Detailed technical documents, operating instructions, electrical installation drawings and related materials should be provided at the same time when delivering the equipment to the buyer;

4. The unmentioned matters shall be resolved through negotiation between the two parties.

Attachment 1: Test block diagram of transformer comprehensive test system (transformer of 33kV and below)

HZ-IV Transfotmer Test Bench