Regarding the power distribution in the factory: overload protection for Phase I and Phase II electricity, as well as start-up overload control for large motors
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As the title suggests: Our company’s power supply and distribution method is as follows; please point out any misunderstandings: The 110KV buses in sections I and II enter the 110KV substation (which is staffed), from where 37.5KV voltage is supplied to 11 35KV substations (which are unstaffed). Depending on the load and distribution requirements, 6KV voltage is derived from the 35KV substations and sent to 13 6KV substations. Distribution or transformation equipment is installed in these 6KV substations to supply large motors with 185KW of power at 6KV, as well as devices with a power rating of less than 160KW powered at 380V, and lighting systems powered at 220V. With this distribution method, 1: How can we prevent the regional substations from tripping due to overload? If motor A is connected to circuit I, and another high-power motor A is started, how can overload tripping of circuit I be prevented? 2. Since both the 35KV and 6KV substations are unattended, is the load signal displayed at the main substation? 3. To prevent the increased load during the startup of large motors from causing the power distribution system to activate its overload protection mechanism (tripping), thereby disrupting production, what are the requirements regarding the power distribution capacity? 4. What size of motors require a soft starter? 5. What is the difference between soft starting and variable frequency starting for soft starters (such as large axial flow fans)?
1. It’s a rather general statement; it depends on what protection value is set for section I, what load you’re carrying, and what the values of the coefficient and the simultaneous coefficient are. 2. Unmanned substations generally transmit local signals to higher-level manned substations. 3. To prevent overload during the startup of large motors, a delay protector must be installed on the circuit breaker. 4. This mainly depends on the quality of the power supply and one’s own requirements; sometimes even very small motors require soft starting and frequency conversion. 5. The starting current of soft start is still nearly twice the rated current compared to that of frequency conversion starting; soft start does not allow speed control, while frequency conversion does enable speed control. However, soft start is cheaper, so it depends on what the client prioritizes.