The JNB-1 transformer protection switch box is suitable for use in distribution networks with AC 50Hz, rated voltage of 380V, and rated current up to 630A. It is used for overload and short circuit protection on the secondary side of outdoor public distribution transformers, and can also be used for infrequent disconnection and circuit use under normal circumstances.

型号 Model	额定电压V Rated voltage	频率Hz Frequency	极数 Number of poles	在环境下额定电流 A Rated current in the environment	额定极限短路分断能力kA Rated ultimate short-circuit breaking capacity
DZ20-630	380	50	3	630、400、500	42

周围空气湿度 Surrounding air humidity	试验电流 Test current	试验时间与结果 Test time and results	超始状态 Super initial state
	1.05in	2H内不脱扣 Not tripped within 2 hours	冷态 Cold state
+30±℃或+70±3℃	1.30in	内脱扣除 Internal deduction	热态 Hot state
任何合适湿度 Any suitable humidity	3in	可近回时间<10S Near return time<10S	冷态 Cold state
	5in或10in	>0.2S	冷态 Cold state