XL-21 series of low-voltage distribution cabinets used in industrial and civil architecture. communication frequency of 50 hz, low voltage 500vand below, three-phase four-wire power system of power distribution and lighting distribution. The line overload, short circuit and leakage protection and to normal conversion circuit. This product is a indoor closed device. its for IP30 protection grade, according to user requirements can be produced degree of protection IP54. Product conforms to standard GB7251.1, IEC60439-1 standard. etc.