HZLY-200A is equipped with a 150kW electric heating system, divided into two independent control groups, with a heating load as low as 2.5W/cm ². There are specific technical meanings behind these two numbers. Only by understanding them can we understand why the heating temperature cannot be adjusted arbitrarily, as well as the benefits of independent control of the two heating groups.

Why does the heating load need to be as low as 2.5W/cm ²

The heat load on the surface of the heater (W/cm ²) determines the surface temperature of the heater. If the heat load is too high, the surface temperature of the heater will be much higher than the average temperature of the oil - taking an electric heating tube as an example, if the heat load is 5W/cm ² and the oil temperature is only 70 ℃, the surface temperature of the heating tube may reach over 150 ℃.

At local high temperatures above 150 ℃, insulating oil will undergo thermal cracking, producing low molecular weight hydrocarbon gases (methane, ethylene, etc.), and in severe cases, even acetylene. Once these cracked gases dissolve into the oil, they will appear in the subsequent DGA analysis of the transformer, interfering with the judgment of the transformer's condition.

HZLY-200A controls the heating load at 2.5W/cm ², ensuring that even at the highest working oil temperature of 80 ℃, the surface temperature of the heater will not trigger oil cracking, fundamentally avoiding false DGA data generated by the oil filter.

The actual value of two independent controls

150kW is divided into two independent control groups, each with 75kW. The benefits of this design are:

One is to start in stages: when the chiller starts, a large amount of cold oil enters the heater. If it is heated at full power at once, the local temperature difference will be large; Group start, you can use one group for preheating first, and then start the second group to reduce thermal shock.

The second is flexible adjustment: when the oil volume is low or the ambient temperature is high, a single set of 75kW can maintain the target oil temperature without the need for two sets to be fully opened; When processing large quantities of low-temperature oil, fully open both sets to shorten the heating time.

The third is to ensure continuity: the failure of one set of heaters does not affect the continued operation of another set, and the equipment can continue to operate with reduced power instead of completely stopping and waiting for maintenance.

Range description of working oil temperature

The working oil temperature range of HZLY-200A is 20-80 ℃, and the optimal dehydration and degassing efficiency oil temperature is usually set at 50-70 ℃. Low temperature, high oil viscosity, and difficulty in degassing; The temperature is too high, approaching the flash point (the flash point of transformer oil is usually ≥ 130 ℃), reducing the safety margin, and the high temperature accelerates the oxidation of the oil.