HEAT SOLUTIONS WHEN TESTING THE MBA BEFORE DELIVERY

HEAT SOLUTIONS WHEN TESTING THE MBA BEFORE DELIVERY

img30-08-2024

Training document

Currently, some large-capacity transformers use oil circuits to lubricate the transformer equipment. When operating, the temperature of this oil circuit can reach ~ 55 °C, causing the oil to change state. Therefore, during the transformer testing process, lowering and maintaining a stable oil temperature is necessary. Understanding this problem, CNV Group would like to introduce a sample of a water-cooled transformer testing cooling system to readers.

SYSTEM REQUIREMENTS:

  • System outlet temperature: 15~55 °C, tolerance ± 2°C
  • The system output water flow rate (MBA input) is: 200~ 600 liters/minute
  • PLC and HMI control systems are capable of recording flow parameters – input/output temperature of the transformer and can export to files.
  • The system is mounted on 2 mobile vehicles and can be lifted or moved by forklift.

To achieve the above requirements, contractor CNV Group provides the following solutions:

1. System schematic diagram:

Picture 1. System schematic diagram – By: CNV Group

2. Working principle

2.1. Phần hệ thống làm mát

– The system is mounted on two steel frames for easy mobility, storage, and transportation when not in use. One steel frame structure – without wheels – is used to place the chiller and valve system, the remaining steel frame contains the pump system and intermediate water tank. The division into two steel frame structures optimizes the frame size (smallest possible size). When needed, these two steel frames are craned and transported to a location outside the inspection room, and connected to the transformers with insulated flexible pipes.

– The system is divided into 2 basic cooling water circuits:

  • The first water circuit includes Chiller equipment, an auxiliary pump for the chiller, heat- exchanger. Accordingly, the chiller equipment will provide cold water in the range of 10~15°C, this water part exchanges heat with water in the tank through the Heat Exchanger, ensuring to maintain a stable water temperature in the tank at ~ 20°C. This is a closed water circuit, ensuring the chiller operates stably with the Chiller Inlet: at 10°C and Outlet: at 15°C
  • The second water circuit includes an intermediate water tank, an auxiliary pump for the transformer, a transformer, 3-way solenoid valve device. Based on the temperature and water flow requirements for the transformer, the 3-way valve device will automatically calculate the opening required to mix the return water flow from the transformer and the available 20°C cold water flow in the intermediate tank to create the required cold water temperature. At the same time, the auxiliary water pump also adjusts the corresponding frequency to provide the water flow required by the user.

– The Chiller will operate based on the signal of the temperature sensor located at the bottom of the tank and the flow meter at the inlet of the chiller. The chiller will operate when the temperature in the bottom of the tank is greater than 20°C (>20°C) and the flow switch detects water entering the chiller. The chiller will turn off when the water temperature in the bottom of the tank drops below 20°C (20°C).

2.2. Phần hệ thống điện điều khiển và giám sát hệ thống

2.2.1.Control system part

The control system includes 01 electrical cabinet to supply power and control the system. On the cabinet body, there is 01 HMI screen to monitor the working status of the equipment, allowing setting of temperature and input flow of the transformer…

The control system is divided into 2 parts (Primary – Secondary):

Primary: to maintain the temperature in the water tank at 20 degrees Celsius.

  • Monitor temperature, pressure, and water flow signals in the Chiller outlet pipe and monitor temperature and water level signals in the tank.
  • Control the Chiller + pump on/off based on the monitored sensor signals, ensuring the water temperature in the tank is 20 degrees Celsius.
  • The chiller has 4 compressor levels – equivalent to 4 levels of Chiller capacity adjustment (25% – 50% – 75% – 100%). Based on the cold water temperature signal from the tank to the chiller’s inlet, the chiller operates continuously and automatically calculates the appropriate compressor level to meet actual load needs.

– Secondary: Purpose to ensure circuit output water requirements (MBA input) according to setup.

  • Monitor the temperature, flow, pressure signals at the circuit outlet (MBA input) and the temperature monitoring signal at the circuit inlet (MBA output).
  • Control the output temperature of the circuit (MBA input) within the range of 15 ~ 55 degrees C. The control method uses a linear electric valve to control the mixing between the 2 types of input water of the circuit (tank and MBA output) to reach the desired threshold.
  • Control the output flow rate of the circuit (MBA input) within the threshold …, The control solution uses an inverter to control the speed of the water pump motor circulating in the circuit.

2.2.2. Phần hệ thống giám sát, xuất dữ liệu:

– The local monitoring system is monitored via the HMI screen on the electrical cabinet surface.

– Remote monitoring system via installed Camera records the indicators on the HMI screen.

– Data extraction via Module, data can be saved for about 1 week with a frequency of 15-30 minutes per data storage

The temperature and water output speed adjustment in the circuit is performed on the HMI screen on the control cabinet surface.

Picture 2. MBA cooling system – By: CNV Group

HVAC Team – Project Division of CNV Group