REZISTOR PUNCT NEUTRU

REZISTOARE PUNCT NEUTRU

NEUTRAL POINT RESISTORS

EGE, spol. s r.o. České Bud ějovice www.ege.cz

ELA T 124.3 en

Neutral Point Resistors for 22kV electrical network .

Related Standards

ANSI/IEEE Std 32-1972 Requirements of IEEE standard, terminology and electrical testing procedure for equipment used for electrical network grounding.

ČSN EN 60529 IP (Ingress Protection) Codes ČSN 33 2000 Protection against electric chock

Terminology

• Neutral Point Resistor (NER) is intended to connect the transformer neutral point to earth.

• Intermittent loading means a loading of a shorter period than it is needed for the temperature stabilization and at the same time the no-load periods are long enough for the resistor to cool down to the ambient temperature.

Use

NER is used to connect the transformer neutral point to earth within HV power supply networks, which are operated as resistance-grounded networks. The purpose of the resistance-grounded neutral point is to suppress overvoltages at earthfaults as well as to provide sufficient current needed to activate protective relays, ensuring a quick disconnection of the faulty section of the power supply network. The power supply networks with resistance-grounded neutral point are supposed to be used in cable networks of big industrial centres. NER is designed for intermittent load. There are also resistors by which the permanet current is stated, in this case the resistor could be loaded with this current continuosly.

Design

NER is designed for outdoor applications. It consists of a housing made of galvanized steel plate. In this housing there are resistive elements arranged vertically one above the other in blocks. The blocks of resistive elements are separated by insulators attached to the sides of the housing. The cooling of the resistor is ensured by natural air circulating inside the housing. The air holes are placed on the front and the back side of the housing. The input bushing for connection of the resistor to the transformer neutral point is placed on the roof of the housing and it is labeled D1. The output bushing for connection to the grounding system of the transformer station is placed in the bottom side of the housing and it is labeled D2. Inside the housing there are installed two current transformers providing curent signals for protection relays. Measuring current transformer T1 is intended for over-current protection and measuring transformer T2 is assigned to be connected to the frame-leakage protection. At the bottom side of the housing there are two cable glands for the current transformers connection.

NEUTRAL POINT RESISTORS

EGE, spol. s r.o. České Bud ějovice www.ege.cz

ELA T 124.3 en

For the proper functionality of the frame-leakage protection it is necessary to isolate the housing of the resistor from earth (e.g. paperboard, fibreglass boards insulation etc.). The anchor bolts must be screwed using insulating washers. The insulation resistance between the housing and earth should be at least 10 Ω.

Working conditions

NER is intended to be used on sites with no protection against climatic impacts, in areas corresponding to the middle category of climates M (CT,WT,EDr and MWDr) with air temperature from -30°C to +40°C and sea level up to 1 000m, with standard level of pollution usuall in city agglomerations with industry spred over the whole area, on sites with sand and dust sources including city areas, on sites protected against considerable vibrations and shocks. In case the resistor is installed inside a closed room, sufficient air circulation must be ensured.

Labeling

Bushing labels: a) input bushing label - D1, b) output bushing label - D2.

Rating plate with technical data:

a) manufacturer designation, b) type designation, c) serial number, d) rated voltage, e) rated current / rated loading time, f) ingress protection code, g) cooling method, h) weight, i) year of production.

Tests

Tests are carried out according to the standard ANSI/IEEE Std 32-1972. The tests results – measured values are stated in the test report.

Surface protection: hot dip galvanizing

Screw stock : stainless steel (A2)

Accompanying documentation

The accompanying documentation consists of: a) technical description, b) certificate of quality and completion of the resistor, c) packing list, c) test report.

NEUTRAL POINT RESISTORS

EGE, spol. s r.o. České Bud ějovice www.ege.cz

ELA T 124.3 en

Final acceptance test

The final acceptance test takes place in EGE manufacturing plant, in case it is stipulated in the purchase contract. Unless otherwise agreed, the acceptance test consists of standard routine tests.

Transport

During tranportation it must be seen to it that the resistor is secured against movement and mechanical damage. Furthermore the transport should be carried out without any falls and heavier shocks. In case transport conditions differ from the above mentioned conditions, an agreement between the manufacturer and the supplier on appropriate measures is necessary.

Storage

NER must be stored only in the climatic conditions as mentioned above.

Maintenance

Before putting into operation it is necessary to tighten all screw connections. It is recommended by the manufacturer of the resistor to carry out a visual examination every two years and check if all screw connections are tightened properly. The periods for insulators cleaning have to be decided by the operator in conformity with local circumstances and pollution degree.

Installation

For the installation of the resistor it is necessary to prepare a concrete foundation with holes of cca 40mm diameter and 200mm depth for the anchor bolts. Before the installation fill the holes with concrete and then put fibreglass pads on the holes and place the resistor on them. Push from above anchor bolts through the holes of the resistor frame and seat them in the concrete. Centre the anchor bolts in the frame by insulating rings and arrange the insulating pads. After the concrete became hard, put upper insulating washers on the anchor bolts and screw the resistor on the foundation.

NEUTRAL POINT RESISTORS

EGE, spol. s r.o. České Bud ějovice www.ege.cz

ELA T 124.3 en

Dimensions

REZISTOR PUNCT NEUTRU

REZISTOR PUNCT NEUTRU - STANDARD:

Type NER 300/22 NER 300/30/22

NER 450/22,5/22

NER 600/30/22

NER 1000/50/22

Electrical network

voltage[kV] 22 22 22 22 22

Rated voltage [kV] 13,3 13,3 13,3 13,3 13,3

Rated current [A] 300 300 450 600 1000

Loading period [s] 6 6 6 6 6

Continuous current [A] 0 30 22,5 30 50

Rated resistace

[Ω] 44,3 ±10% 44,3 ±10% 29,5 ±10% 22,1 ±10% 13,3 ±10%

Rated frequency

[Hz] 50 50 50 50 50

Current transformer

T1

300/5 A, 30VA, 1FS5

300/5 A, 30VA, 1FS5

400/5 A, 30VA, 1FS5

600/5 A, 30VA, 1FS5

1000/5 A, 30VA, 1FS5

Current transformer

T2

100/1 A, 15VA, 1FS5

100/1 A, 15VA, 1FS5

100/1 A, 15VA, 1FS5

100/1 A, 15VA, 1FS5

100/1 A, 15VA, 1FS5

Ingress protection IP 23 IP 23 IP 23 IP 23 IP 23

Cooling AN AN AN AN AN

Type NER 300/22 NER

300/30/22 NER

450/22,5/22 NER

600/30/22 NER

1000/50/22 A [mm] 1400 1450 1370 1450 1410 B[mm] 1320 1450 1430 1450 1430 C [mm] 1770 2170 2560 2170 2950 D [mm] 1150 1150 1000 1150 1040 E [mm] 900 900 900 900 900 F [mm] 1180 1190 1040 1190 1080 G [mm] 1140 1140 1140 1140 1140 H [mm] 400 380 380 380 380

I M16 M16 M16 M16 M16 J M12 M12 M12 M12 M12

Weight [kg] 356 480 540 465 645

NEUTRAL POINT RESISTORS

EGE, spol. s r.o. České Bud ějovice www.ege.cz

ELA T 124.3 en

EGE, spol. s r.o. Novohradská 34

370 08 České Bud ějovice Czech Republic

www.ege.cz

Tel.: 00420 38 77 64 428, 412 Fax.: 00420 38 77 64 603 E-mail: elaobch@ege.cz