Regarding the setup of overload protection in electrical systems, is it installed at the main transformer, at the motors, or elsewhere?
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For example: Power is transmitted from the 110KV main substation to the 35KV local substation, from where 6KV, 380V, and 220V voltages are supplied for power and lighting purposes. The known overload current is 2KA, while the operating current is 1.8KA. If another motor is started (with a rated current of 0.1KA and a starting current of 0.4KA), then: 1. How can it be ensured that the circuit does not trip? Should a delay protection device be installed? 2. If the motor being started has a rated current of 0.4 KA and a starting current of 1.2 KA, then a trip will inevitably occur. How can such incidents be prevented? 3. How is the tripping protection configured, from the total variable to the individual sub-variables? I am looking for relevant information. 4. In factory power supply, can the main power source meet the full-load power requirements of all electrical equipment as well as the power demands during instantaneous starts? What are the requirements and specifications for the power capacity design?
5. How to prevent a short circuit in a single motor from causing the main transformer to trip? Is the delay protection time different?
The set values of these systems are determined based on the system’s short-circuit capacity and short-circuit current, so the second situation you mentioned will not occur. Moreover, each motor is equipped with appropriate protectors, which reduces the likelihood of cross-level tripping
But bypass tripping still occurred, and not just once. What are the preventive measures, guidelines, and methods?