Factory Price Dgnpd - Type Transformer Neutral Point Grounding Protection Device

• Breaking Capacity: High Voltage Circuit Breakers
• Operation: Manual Type
• Arc-extinguishing Medium: Vacuum
• Installation: Fixed
• Type: Circuit Breaker
• Function: Conventional Circuit Breaker, Overcurrent Protection
• Model NO.: DGNPD
• Ambient Temperature: -40ºC-+40ºC
• Altitude: Not Over 3000m
• Power Grid Frequency: 48 ~ 52Hz
• Relative Humidity: Not Higher Than 90% (25ºC)
• Transport Package: Export Box
• Trademark: DGG
• Origin: China
• HS Code: 8504311000
• Production Capacity: 100000PCS/Year

Product Description

PHOTOS OF PRODUCT

GENERAL 

110kV and above power systems adopt the operation mode of neutral point direct grounding, commonly known as a high current effective grounding system. The neutral point of the transformer in operation is directly grounded, so there is no overvoltage and protection problem with the neutral point. However, in actual operation, in order to limit single-phase short circuit current, prevent communication interference, relay device setting configuration, and other requirements, the operation mode of ungrounded neutral points of some transformers is often adopted. Generally, only 30%~50% of the transformer neutral points are allowed to be directly grounded, so as to ensure the safe and stable operation of the system. In addition, in some ring or radial power supply networks, the dispatcher controls the power flow direction according to the operation needs and consciously arranges the neutral point of a certain intermediate terminal transformer to operate in a non-direct grounding mode. Obviously, under the condition of three-phase symmetry in the normal operation of the system, the neutral point potential is zero regardless of whether it is grounded or not, and there is no need to take overvoltage protection measures. However, in operation, it is often interfered with by various factors (such as lightning, operation, refusal to move, disconnection, single-phase grounding fault, etc.), and the neutral point of the transformer will have high overvoltage and be damaged, so it must be protected.

The electric power industry standard DLT620-1997 Overvoltage Protection and Insulation Coordination for AC Electrical Installations stipulates that "local ungrounded systems should be avoided in 110KV and 220KV effectively grounded systems, and excessive power frequency over-voltage should be generated. For such partially ungrounded systems, the over-voltage protection of 110kV and 220kV ungrounded neutral points with power supply on the low-voltage side should adopt the method of zinc oxide lightning arrester plus parallel clearance"

DGNPD series transformer neutral point gap grounding protection complete device (hereinafter referred to as the complete device) produced by our company is a complete device developed to protect against the damage of transformer neutral point insulation transformer overvoltage, switching overvoltage and power frequency [transient] overvoltage.

MODEL AND MEANING
USAGE ENVIRONMENTAL CONDITIONS

1. Outdoor Use
2. Ambient Temperature: Not lower than -40ºC, not higher than +40ºC
3. Relative Humidity: Not higher than 90% (25ºC)
4. Altitude: Not over 3000m
5. Power grid frequency: 48 ~ 52Hz (50Hz systems), 58 ~ 62Hz (60Hz systems)
6. Installation site: the air shall be free of chemical corrosive gas and steam, and explosive dust.

TECHNICAL SPECIFICATION
 

Product Code	Transformer's Neutral point withstand level		Zinc oxide arrester				Discharge barrier	Isolation Switch
	1.2/50μs Lightning Impulse Withstand Voltage (peak value) (kV)	1 min Short-time Power frequency withstand Voltage(kV)	Rated Voltage (effective value) kV	Special long-distance voltage (effective value) kV	DC 1mA reference voltage is not less than	8/20μs 1.5kA lightning impulse current residual voltage is not less than kV	Power frequency discharge voltage (effective value) ± 5% kV	Rated Voltage	Peak Value Withstand Current (kA)	10s Short-Time Withstand Current (kA)
DGNPD-85/180-60	180	85	60	48	86	144	67.5	400	15.5	4.2
DGNPD-95/250-72	250	95	72	58	103	186	81	400	15.5	4.2
DGNPD-140/325-96	325	140	96	77	137	260	108	400	15.5	4.2
DGNPD-140/325-102	325	140	102	82	158	260	115	400	15.5	4.2
DGNPD-200/400-144	400	200	144	116	205	320	162	400	15.5	4.2
DGNPD-230/500-207	550	200	207	166	292	440	234	630	50	20