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.     Industrial Resistor                                                           

We Seonjinhitech is the original company of the industrial resistors in Korea. Our design, manufacturing, and production technology for resistors boasts the highest level in the domestic industry. In addition, as an EPC company that designs, manufactures, and constructs of all products with our own technology, we have  established a customization system that can supply customized products to customers in a timely manner, and continuously develops and supplies new products that are appropriate for the rapid changes in the industry.

  ◑  Element types of industrial resistor                                                                                

V-W grid type (VW) ( 10~50Ω )	Edge Wound type (EW) ( 50~100Ω )	Heli-Wire type (HW) ( 50~300Ω )
		
SUS grid type (SG) ( < 10Ω )	Wire Wound type (WW) ( for fine resistance )	SUS tube type (ST) ( for hi-voltage, hi-power )

  ◑  Supply Procedure (Ex. Load Bank)   

   ◎  Process   

   ◎  Output materials by step   

Step	Process	Activity	Output	Remark
1	Reception of customer   request	Review of basic requirements received.    Confirmation of production and supply    conditions	RFQ data
2	Basic Specification    Design	Basic configuration and specification design,   Customization requirements design	Draft TDS/TS
3	System configuration    and operation control    plan design	Setup of system operation & control plan,   GA design of operation & control panel   Basic design of operation & control panel    Estimation of required materials (BOM)	Draft Op’ plan   Draft Op’ panel GA   Draft control logic   Draft BOM
4	Submit a quote and    proposal	Basic design (BD drawing),   Setup of technical specifications,   Setup of production and supply conditions,   Analysis of purchase and manufacturing cost,   Submission of quotation and proposal	Offer Sheet   Proposal Doc.   BD drwings   TDS/TS
5	Purchase order review   and supply contract	Review of contract (purchase order)   Confirm the supply terms     (FOB/CIF/CFR/DAP/DDP)   Sign the contract (counter sign)   Provide the  deviation sheet (if required)	Contracts (PO)   BD drawing   TS/TDS   BOM
6	Submission of Approval    Documents	Detailed design   Compose of technical specifications (TS)   Submission of approval documents	Approval drawing   Technical Data Sheet   Technical Spec.
7	Approval of Design    Document	Reflection of comments on approval doc.   Resubmission of revised doc. for re-approval   (DCN matters are submitted separately)	Revised drawings   Revised spec.   DC Notes
8	Procurement and    production	Purchase order for manufacturing   production	Required material list up   Main parts / sub materials /   Accessories   Self-made, OEM manufacturing,   Self-test PAT	Separate order for purchasing materials    (main parts, sub materials, accessories)     Manufacturing/processing sub-assembly (inspection)    Medium/large assembly (unit functional test)   iTP submission/approval  Factory/Shop test report
9	Inspection & test	Submission of ITP    Customer witness test & inspection   Type test by certified agency (if necessary)	Additional ITP check    Routine Test Report   FAT, FAC   Type Test Report (if required)	Customer witness test   Test Report Issuance   Type test by certified Agency (if necessary)   Environment/Durability test   Function/Performance Test,    Certificate Issuance
10	Packing, shipping and   delivery	Ex-works inspection   Export packaging (if necessary)   Shipping   (Domestic, overseas: Import/Export    procedures)	Products   Final doc.(Drawing,TS, manual)   Packing List,  Bill of Lading     Certificate of Origin   Commercial invoice	Ex-works inspection sheet (sizing, weighing, Ex-work sheet)   Packaging: domestic (Simple), overseas (export packaging)   Transportation, Delivery (FOB, CIF, CFR, DAP, DDP)   Land / Sea / Air transportation   Issue of related Documents (PL, BL, COO, CI.)   Delivery, receipt confirmation

Industrial load resistors (Load Bank Resistors) are equipment that generate artificial loads (power consumption) for performance testing of electrical equipment, generators, UPS, etc. Those are operated like an actual loads by consuming power as heat and are used for inspection, maintenance, and test runs of equipment. In particular, they are equipment that must be installed in places where emergency power is essential, such as factories, hospitals, and data centers, to ensure the stability of the power system. The resistor elements are mainly made of Ni-chrome or iron chrome that can withstand high-power and high-temperature environments, and are made into wire or flat shapes.

Out door type LDR	Indoor type LDR

  ◑  Featutres   

  ◑  Basic Circuit Drawing   

  ◑  Enclosure   

  ◑  Selection of LDR Specification   

Neutral grounding resistor (NGR) is a resistor used to ground the neutral point of a transformer or generator. It is used to limit the fault current flowing when a ground fault occurs in a three-phase power system to a specified value or less, which plays an important role in reducing damage to electrical equipment and the risk of fire. NGR is mainly used in high-voltage systems and performs detection, blocking functions simultaneously by linking with a protection relay. It is usually manufactured in a coiled form using a metal wire that is resistant to high heat, & in the case of large-capacity, low-resistance, it is manufactured in a grid form by cutting SUS plate. The housing is designed and manufactured for indoor use, outdoor use, and waterproof/dust-proof structure depending on the installation conditions.

  ◑  NGR Out Look   

Outdoor type NGR	indoor type NGR

  ◑  Effects of NGR installation   

√  Prevents insulation breakdown of equipment and lines due to abnormal voltage in case of a single-line ground fault 

    (reduces insulation level of lines and related equipment)

√  Prevents linked accidents by temporarily blocking abnormal over voltage

√  Restricts the level of potential hazardous fault current

√  Ensures safety for related systems (GEN, TR, Motor, etc.) and personnel

√  Reduces arc exposure and generates alarms in case of a ground fault

√  Provides optional ground fault detection tripping level

√  Detects fault circuits and measures fault currents using CT and ground fault protection relay (OCGR)

√  Function to suppress inductive faults in communication lines in case of a ground fault

√  Prevents sudden changes in load in case of a generator ground fault

  ◑  Types of neutral grounding way  

none grounded type		directly grounded type	Resistance grounding type	Reactor grounding type
Zn= ∞   No grounding wire   Applicable to general distribution sys.   (~3.3kV, 6.6kV)   Maintains high impedance to the neutral point   Small ground fault current allows transmission   even  in the event of momentary ground fault   Less inductive interference in communication    lines   Ground fault relay malfunctions frequently   Can be operated as V-connection when 1 line   is faulted in Δ-connection.		Zn=0  Direct grounding with conductor   Applicable to ultra-high voltage   (>15kV) systems   Almost no voltage increase in the   healthy state,    Protective relay operation is reliable   Reduction of insulation level of related    equipment,   Large inductive interference in    communication lines   Very large fault current in case of    ground fault	Zn=R   High resistance: >100~1000Ω(5~100A)   Low resistance: <30Ω (>200A)   Restricts fault current to a specified   value or less.   The resistance value is selected so    that the ground voltage of the healthy   part does not exceed 1.3 times the   normal voltage in the event of a single    line ground fault. If the resistance is    too large, the relay operation becomes     difficult and the ground voltage of the   healthy part increases.	Zn= jXL  Applied to medium-distance    transmission lines (66kV)   Initial fault current protection function.   Applied with L value that can resonate   in parallel with the line ground           electrostatic capacitance.   Power transmission is possible even    in the event of a ground fault.   Less inductive interference on   communication lines. Stability   Excellent, but maximum abnormal   voltage in case of a fault.   Low reliability of protective relay    operation

   ◑  NGR configuration according to transformer wiring   

in case of the transformer  secondary is Y-connected	in case of the transformer secondary is Y-connected
Install NGR directly on the neutral point    of the secondary side of the transformer,   Install CT, DS, relay (51N) as needed to   improve safety protection and operability.	Use a grounding transformer (GTR) for grounding on the secondary side of TR and connect the NGR     to its neutral point. Since GTR operates only in the event of a fault such as a ground fault,      it is usually designed with a short-time rating.
TR 2'ry neutral point grounding	TR 2'ry open type,  Δ -TR grounding	Zig-Zag TR neutral point grounding	Generator neutral point grounding

  ◑  NGR Protection Circuit   

Generally, the NGR value is set so that the ground fault current is limited to 5~100 (high resistance) and 200-300A (low resistance) in the case of a 1-line ground fault. The ground fault current is detected by the ground over current relay 51N, and the NGR is protected by displaying an alarm and tripping the circuit breaker on the power side when the time is less than the rated time of the NGR.

 < Configuration of NGR Protection circuit >

  ◑  NGR Configuration (Application Cases)  

< Remote monitoring & manual control NGR >                                        < Electric drive type remote control NGR >

< Self-controlled NGR by self-GTR and relay >

  ◑  Basic Structure of NGR    

  ◑  Selection of NGR Spec.   

   ◎   Considerations when selecting the NGR Spec.   

√  Line-to-line voltage (VL) or phase-to-phase voltage (Vs) of the main transformer

√  Continuous operating time and maximum current criteria

√  Short-time rating check: Typically applied for 10 seconds, 30 seconds or 60 seconds

√  Continuous rating check: Typically applied at 5% to 10% of full load current

√  Maximum current that can flow in cold condition

√  Insulation class specified based on line-to-line voltage

√  Refer to the maximum short-time temperature rise of the resistor as 760°C according to IEEE Std 32-1972

     (Requirements for Neutral Grounding  Resistance)

√  Check the protection IP rating for outdoor or indoor enclosure: Standard enclosure applies IP10, IP13 or IP23

√  Enclosure material can be mild steel, powder coated finish or hot-dip galvanized, stainless steel

√  Whether auxiliary items CT, VT, DS, GTR or other options are applied

   ◎   Selection of NGR Spec.   

※   Calculation of NGR resistance : Rg = (Line V÷√3)÷Rated Current

 Ex.> When Line VL : 6600V,  Rate current IR : 100A

Then NGR resistance Rg will be calculated as bellow ;

 ∴   Rg = (6600/√3)/100 = 38.1 Ω

   ◎   NGR Usage Time Rating   

√  It refers to the time it takes for the surface temperature of the resistance element to rise to the rated allowable temperature,

√  It is stable for the system equipment to set it slightly longer than the ground fault detection and interruption device of the power line.

√  Short-time rating is generally used as 10 sec, 30 sec, 60 sec, <10 min for the ground fault current flowing to the neutral point,

√  Duration rating is set to an average of >10 min.

   ◎   Temperature rise limit of NGR   

Rated Using time	temperature rise limited	Standard	Remark
Short time rate (<10min)	760°C	IEEE 32(1972)
Short time rate (<10min)	750°C	KISC	국 내  기 준
Delay time rate (Average 10min)	610°C	IEEE 32(1972)
Delay time (Average 10min)	450°C	KISC	국 내  기 준
Continuous time rate	385°C	IEEE 32(1972)
Continuous time rate	350°C	KISC	국 내  기 준

   ◎   Rated current and appearance spec. by voltage   

정격전압 (kV)	정격전류 (A)	정격사용시간 (sec)	온도상승한도 (℃)	width (mm)	Depth (mm)	Height (mm)
3.3 /√3	100	10 / 30	350 / 750	600	445	630
	200	10 / 30	350 / 750	600	445	630
	400	10 / 30	350 / 750	600	625	870
6.6 /√3	100	10 / 30	350 / 750	600	535	630
	200	10 / 30	350 / 750	600	625	950
	400	10 / 30	350 / 750	600	715	1190
11.6 /√3	100	10 / 30	350 / 750	705	800	1200
	200	10 / 30	350 / 750	705	900	1200
	400	10 / 30	350 / 750	705	900	1560
22.9 /√3	100	10 / 30	350 / 750	705	1020	1560
	200	10 / 30	350 / 750	705	900	1920
	400	10 / 30	350 / 750	705	1400	1920

   ◎  Calculation of GTR capacity (Real case)   

      ( According to Westinghouse Data )

1)  3phase Equivalent Power Capacity, Equivalant power (kVA)

Pa = V / √3 * Ig * K_f

V : Line Voltage (kV)

Ig : Earthing Current (A)

K : Factor (%),  (NPCCR - Neutral Point Continuous Current Ratio to ground fault current)

2)  K Factor

Duration (time rate)	Ratio of neutral point continuous current to ground fault current (%)
	0~5%	10%	15%	20%	25%
< 10 sec	0.11	0.11	0.157	0.206	0.264
~  1 min	0.112	0.141	0.18	0.223	0.269
~  10 min	0.206	0.233	0.26	0.283	0.32
> 10 min	0.602	0.608	0.619	0.633	0.65

3)  Calculation of GTR Power Capacity (Example)

☞.  Condition of NGR Specification

Rate Voltage - V :  6.6 / √3 kVA

Earthing Current - Ig  : 100 A

Resistance - R :  38.1 Ω

Duration time :  30 sec ( < 1 min )

K Factor : 0.269 at 30 sec, and 25% of NPCC ratio (harsh condition)

☞.  Calculation of GTR Capacity

Equivalent Capacity Pa (kVA) 

= V / √3 * I_g​ * K_f

= 6.6 / 1.732 * 100 *0.269

= 102.5 kVA

∴    Required a 100 kVA GTR

  ◑  NGR test and Evaluation