Power Resistors

Power Resistors
Power Resistors
Power Resistors Rev. 07.2014
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MV Technology Solutions
Company Overview
MV Technology Solutions is a distributor of specialised materials and equipment for the electricity supply, rail and industrial markets
throughout Australasia.
Our Primary Customers Include
 Transmission and Distribution
 Power Stations
 Rail and Tramway Infrastructure
 Rail Rolling Stock
 Electrical Contractors
 Electrical Wholesalers
 Industrial and Mining
MV Technology Solutions is committed to engaging with customers with the aim of supplying products, support and services that meet
their specific requirements whilst maintaining a focus on their future needs. This is underpinned by our commitment to research and
development, and identifying suppliers that conform to our high standards of innovation, reliability and quality.
Our staff has the expertise and knowledge to assist with equipment specification and training, as well as providing hands-on service and
support in the field.
Power Product Overview (1kV to 500kV)
 Fault Circuit Indicators
 HV Circuit Breakers
 Reactive-Power Compensation
 Power Factor Correction
 Indoor AIS and Vacuum Components
 Integrated Voltage Detecting Systems
 Insulators and Line Hardware Accessories
 Motor Operating Devices
 AIS Switches and Disconnectors
 Power Resistors
 Ripple Control Systems
 Solvents and Lubricants
 Surge Protection
 Fuses and Fuse Tester Devices.
 HV Testers and Testing Sticks
Power Product Services
 Consultancy Services
 Local Repair /Modernisation Facility
 Installation Supervision
MV Technology Solutions, together with our customers, has been delivering innovative and reliable cost effective projects throughout
Australia and New Zealand. Feel free to contact our friendly team to see how we can assist you:
Ph:
Fax:
Email:
+61 (0) 2 9726 7702
+61 (0) 2 9726 7703
[email protected]
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Contents
Power Resistors
Neutral Grounding Resistors (Wire Wound/Steel Wound)
Generator Neutral Grounding Resistors
High Resistance Grounding (HGR) Systems
Dynamic Braking Resistors
Motor Control Resistors
Anti -Condensation Space (Panel) Heaters
Harmonic Filter Resistors
Current Limiting Resistors
RC Filters
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4 to 6
Neutral Grounding Resisters
Power Resistors
Features:
 Stainless-steel resistor elements
 Current transformer included
 Bolted resistor element connections
 All RAL colours available (RAL 7032 Standard)
 2 mm hot dip galvanised steel enclosure (other available on request)
 High thermal capacity to absorb high currents
 High altitude ratings
 Custom made lifting eyes for secure lifting
 Rugged shock-resistant construction
Description
Neutral grounding resistors are designed to limit the ground fault current to a safe level so
that all the electrical equipment in the power system is protected. The resistor should be the
only current path between the neutral of power transformers or power generators and
ground.
If the neutral of a system is not grounded, it can potentially see a destructive transient
overvoltage from line to ground during normal switching of a circuit having a line-to-ground
fault. It has been proven through experience that these over voltages cause aging on
equipment and failure of insulation at locations on the system other than at the point of the
fault. A relatively unimportant line-to-ground fault on one circuit may result in considerable
damage to equipment and interruption of service on other circuits.
Although it is possible to limit fault currents with high resistance Neutral Grounding Resistors,
phase to ground short circuit currents can be extremely reduced. As a result protection
devices may not sense the fault. Therefore, it is the most common application to limit single
phase fault currents with low resistance Neutral Grounding Resistors to a safe value while at
the same time letting enough current to flow to operate protective relays or fault indicators
that will alarm, clear or assist with the fault.
While there is a disturbance in the power system the resistor must be capable of absorbing
and dissipating the energy generated without exceeding the temperature limits established
by IEEE-32 Standards allowing the fault to be safely limited, isolated, and the power system
is protected against over-voltages.
Example of providing a artificial neutral point if it not possible to reach the neutral
point of the source or for delta connections.
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Example of grounding the neutral
point through the resistance
Neutral Grounding Resistors
Power Resistors
Standard Enclosures:
 2mm hot dip galvanised steel or stainless steel enclosures
 Stainless steel or aluminium enclosures on demand
 Epoxy-based RAL 7032 (or RAL 70XX) polyester electrostatic powder coat paint
 Solid top cover sloped to prevent water accumulation
 Custom made lifting eye bolts for secure lifting
 Removable front cover for easy access to connection and inspection
 Corrosion resistant nameplate
 Can be custom manufactured to suit your requirements
Instruments and other components
 Elevated support stands are provided for ground clearance and safety
 Specially designed units for extreme hazardous environments
 Installation of voltage transformers
 Installation of protection relays
 Porcelain entrance bushings mounted on top or side of NGR (earthing)
 Grounding transformer installation
 Motorised or manual single pole disconnector switches, load bank switches, surge
arresters and heaters in the Neutral Grounding (earthing) Resistors
Technical Specifications
Operation Voltage
Up to 72 kV line to line systems
Rated Current (A)
Up to 5000
Ambient Temperature (°C)
< 55
Resistance Alloy
Stainless-Steel
Protection Degree
IP 23 (outdoor) and others
Standards
IEEE 32, EN 60137,EN 60529, ENISO 1461 ,
EN 60298 ,EN 60273,EN 60071,EN 60060
Sample Dimensions of Neutral Grounding Resistors
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Un (kV)
In (A)
Seconds
Weight (kg)
W x L x H (cm)
36 / √3
1000
5
950
111 x 190 x (210 + 40*)
7.2 / √3
300
60
470
111 x 95 x 160
17.5 / √3
400
10
440
111 x 95 x 160
4.1 / √3
400
10
150
111 x 95 x 70
12 / √3
1000
5
400
111 x 95 x 160
11 / √3
700
10
380
111 x 95 x 210
6.9 / √3
400
10
280
111 x 95 x 160
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Neutral Grounding Resistors
Power Resistors
Routine Test
 Measurement of insulation resistance between enclosure and resistor
 Withstand test of dielectric strength at network frequency for one minute
 Measurement of total DC resistance
 Insulation teat of resistor blocks
 Galvanise thickness teat
 Paint thickness test
Type Tests
 Temperature rise test
 Protection degree test
 Impulse voltage test (1,2/50 µs)
 Measurement of AC resistance
 Seismic test
Selection / Ordering Details
 System Voltage
 Line to Neutral Voltage
 Desired Current Rating
 Desired Resistance Level
 Maximum Time ON (seconds)
 Bushing Entry or Cable Entry
 Current Transformer Ratio (if applicable)
 Disconnector Switch (if applicable)
 Special Options (if applicable)
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Generator Neutral Grounding Resistors
Power Resistors
Features (Up to 13,8 kV 3000 A):

Test terminals for current and voltage transformers secondaries

Circuit diagram included in terminal box

100 W anti-condensation heater included against condensation

Zinc - oxide lightning arresters and surge capacitors on demand

Voltage transformers fuses with signal contacts

M.V. fuse protection
Usage:
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High Resistance Grounding (HGR)
Power Resistors
Features
 0 - 10A analogue ammeter and 0 - 250V analogue voltmeter with setting on panel
 Automatic door switch for power shut down
 Test button to indicate fault
 Green light for normal conditions
 Intermittent alarm and red light during ground fault
 Auxiliary free contacts at pulse and alarm position during fault
 Suitable for 240....4160V three phase systems
 Pulse /Normal Selector switch to magnify current and intermittent pulse during
ground fault.
High Resistance Grounding (HGR) systems are used in power systems where phase to
ground short-circuit current is desired to be limited zero to a few amperes by placing high
resistance between neutral point of transformer (or generator) and ground. As it is not
possible to locate the fault point in delta connected systems, an artificial neutral point is
created and delta connected system can be grounded. This allows a fault current of a few
amperes thus locating the fault point gets easy. When the neutral point is grounded through
high resistance, both continuity of operation is provided during fault condition and sufficient
current (typically between 2A and 10A) flow is provided for ease of locating the fault point.
While locating the ground contact point of phase, ground fault current that is limited to
approximately 2A, generating approximately 10A pulses (approx. 1 second on, 1 second off),
provides ease of measurement thus using short time pulses is the common application in
HRG systems today.
Generally, measurement is performed by analogue and wide clamp ammeters. The clamp
ammeter outside the phase cable is traced until the pulse current disappears on the
analogue display. High Resistance Grounding Systems are an economical and practical
choice, especially systems under 5000 Volts. As zero sequence (3Io) currents flow through
neutral point due to line capacitance of cables, HGR alarm level is set to a point that is
greater than 3Io .
Technical Data
Approximate phase to earth fault current in 240-5000 V networks:
 Solidly grounded systems: 1000-6000A
 Low resistance grounded systems 100-1000A
 High resistance grounded systems : 2-10 A
 Ungrounded (or delta) cable systems: 0,3-2,8 A/km: 2-10 A
 Dimensions (LxWxH)= 60 x 100 x 200 cm
(Other enclosure types available on demand.)
Discharge Currents
Of three phase cables, motors and damping capacitors
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Network
Voltage (V)
Cable
(240mm) 3 (A/km)
Motor
(A/1000HP)
Damping
Capacitors (A)
240....1000
0.3
0.01
---
2400
1.0
0.10
0.78
4200
2.0
0.10
1.35
7200...12000
2.8
0.15
2.25
Dynamic Braking Resistors
Power Resistors
Areas of Usage
Dynamic braking resistors are used to stop AC and DC motors with inverter control. Design of Dynamic Braking Resistors depend
on recommended braking periods or specific applications.
Typical Enclosures:
Technical Properties
Continuous Power (W) :
Upon Request
Power for 6 seconds :
Power for 12 seconds :
Power for 60 seconds :
20x Continuous Power
10x Continuous Power
2x Continuous Power
Voltage:
Insulation Level :
Resistance Value (ohm) :
Cooling:
Protection Degree:
1…3000V
3 for 60 seconds
On demand
Natural
IP20 and others
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Dynamic Braking Resistors
Power Resistors
Tips
Electric motors in certain cases run as a generator by the machine that it is operating and feeds the electric network. If the motor
is required to stop or slow down to nominal speed in such cases, a resistor with suitable ohmic and watt ratings is connected to
inverter braking terminals in order to convert the energy generated by motor to dc current and convert it into heat through
dynamic braking resistor. Required power of a braking resistor (dynamic braking) in order to brake a motor that rotates at
maximum speed and maximum load must be equal to the power of the motor. However, as the braking time is generally around
a few seconds, a resistor power rating that is smaller than motor's rated power can be over loaded for a short time in order to
provide an economical way of braking.
Warning 1
Ohmic value of resistors for braking purposes can not be less than stated dynamic braking resistor manufacturer catalog values.
Otherwise, inverter and resistor can be damaged. If the ohmic value chosen is larger than inverter catalog's recommend value,
braking time gets longer. Braking time is determined by the weight and speed of rotating parts.
Warning 2
If braking time is unknown, as a safety tolerance , the resistor watt rating should be chosen the same as the motor's power
rating.
Example 1
Suppose that an electric motor with a power rating of 100 kW, is lifting a load for 60 seconds and descending the load for 60
seconds with dynamic braking. The operation factor (ED%) for this system will be ED% = 60/(60+60) = 50 % . As a result of this
fact, this braking resistor will operate for 60 seconds and cool down for 60 seconds within the operation cycle of 120 seconds of
the crane. As a result of this fact, a braking resistor that will brake a 100 kW motor for 60 seconds must withstand operating 0,50
x 100 = 50 kW continuously and 100 kW for 60 seconds
Example 2
If a 100 kW electric motor is running 10 seconds and dynamic braking is being applied for 80 seconds within a time frame of 90
seconds, as the braking time is longer than 60 seconds, it is considered as continuous braking and an dynamic braking resistor
which can withstand 100 kW continuously is strongly recommended
Example 3
Suppose a 100 kW electric motor is rotating a fan and after the frequency of motor becomes zero, the fan stops with a braking
resistor at 6 seconds. If the motor will start running after Tr = 54 seconds, a smaller wattage rating for this application can be
selected.
Overload time (Tbr) = 6 seconds
Braking Resistor Power at Overload (Pbr) = Pmotor x Tbr / (Tbr + Tc) = 100 x 6 / (6+54) = 10 kW . So a resistor with a power
rating of 10 kW is enough for his application.
Over Load Multiplier of this resistor (OLM) = (6+54)/6 = 10,
So an 10 kW resistor must withstand the power of 10 x 10 = 100 kW for 6 seconds.
Relationship between Over Load Multiplier / Cooling time / Over Load Time can be seen in the following graph.
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Motor Control Resistors
Power Resistors
Areas of Usage
Overhead cranes
Lift trucks
Machine tools
Conveyors
Cement plants
Industrial controls
Steel mills
Ships and submarines
Types
Designed and tested to applicable IEC and IEEE standards
Designed for all wound motor, squirrel cage motor and induction motors
Durable construction
Stainless steel grid or resistance alloy elements
High performance in heavily polluted areas
Selection Details
Application
Power of motor
Rotor current
Rotor voltage
Starting torque
Number of speeds
Desired starting time (seconds)
Duty cycle
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Anti-Condensation Heaters
For Electrical Enclosures
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High performance in polluted area
DIN Rail mount or flat surface mount
Stainless Steel 35mm DIN rail clip (HR.PTC and HRY series)
Other voltage / power output options upon request
High Reliability
Natural Convection
Durable construction
Condensation can form in a enclosure due to fluctuating temperatures. This can cause serious malfunctions or even component
failure. Anti - condensation space (panel) heaters prevent condensation thru convection.
Type
Width
Length
Height
HRu.100
27 mm
280 mm
19 mm
HR.PTC.50
50 mm
115 mm
50 mm
HR.PTC.100
50 mm
185 mm
50 mm
HRY
100 mm
250 mm
5 mm
HRYr
100 mm
250 mm
10 mm
•
•
•
•
•
•
TYPE PTC
Wide voltage range 110 - 240V AC / DC
Pressure clamp connectors
EN 50022 35 mm rail clip fixing
Heating element consists of a self-regulating PTC resistance
Heater and covers made in natural anodised aluminum alloy
110 – 240 V AC - DC
HEATING
POWER
(WATT)
SURFACE
TEMP.
(◦C)
INITIAL
CURRENT
(A)
HR.PTC 100
100
105
4.5
0.475
HR.PTC 50
50
105
3.6
0.237
TYPE
(*) after 10 minutes of operation
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RATED
CURRENT
(A)(*)
SIZE
(mm)
140
WEIGHT
(kg)
0.40
70
0.25
Anti-Condensation Heaters
For Electrical Enclosures
TYPE HRY and HRYr
 Operation voltage of 240 V and others.
 Over voltage withstand capability up to 300V continuous.
 Compact dimensions (100x250x6 mm).
 Touch-safe advantage with only 60°C temperature rise.
 Welded edges of stainless steel casing for corrosion resistant and moisture proof
resistance elements.
 2,5 meters long heat resistant cable is provided together with the heater as
standard. Longer cables are available on request.
 3 kV / 1 minute dielectric withstand capability.
 DIN 35 rail mounted types on demand.
 Vertical or horizontal mounting capability.
 5 years warranty.
TYPE HRu 100
 240 V 100W.
 Wall mounted model.
 For compact construction
 Max Surface Temperature 60°C
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Harmonic Filter Resistors
Power Resistors
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Reduced neutral currents and resonance
Improved voltage stability
Reduced system losses
Increased equipment life
Reduced phone system interference
Improved system reliability
The purpose of a harmonic filter is to reduce distortions in power systems, produced by non
linear loads such as arc welders, induction furnaces, VFDs, ballasts, computer equipment,
phones, UPSs etc., which can cause failure of motors, transformers and switchgear through
insulation breakdown, arcing and overheating.
In a normal AC power system, supply voltage varies sinusoidally with a fundamental
frequency of 50 or 60 hertz. When linear loads, such as resistive heaters, incandescent
lamps, constant speed induction and synchronous motors, are connected to the system,
sinusoidal currents will be drawn from the system at the same frequency as the voltage.
However, when non-linear loads are connected, a series of sinusoidal currents, called
harmonics, will be drawn at integer multiples of the fundamental frequency.
Electric motors experience hysteresis loss caused by eddy currents set up in the iron core of
the motor. These are proportional to the frequency of the current. Since harmonics are at
higher frequencies, they produce more core loss in a motor than the fundamental frequency,
resulting in increased heating of the motor core, which could shorten the life of the motor.
The 5th harmonic causes a counter electromotive force in large motors which acts in the
opposite direction of rotation. This force is not large enough to counteract the rotation but it
will slow down the motor.
Electric power normally does not interfere with telephone communications because its
frequency is too low but higher-order harmonics can interfere with telephone service if they
became induced in the line.
The increase in transformer eddy current loss due to harmonics has a significant effect on
the operating temperature of transformers. Transformers that are required to supply power to
nonlinear loads must be derated based on the percentages of harmonic components in the
load current.
Many industrial and commercial electrical systems have capacitors installed to offset the
effect of low power factor. Most capacitors are designed to operate at a maximum of 110% of
rated voltage and at 135% of their kvar ratings. Since capacitive reactance is inversely
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Designed and tested to applicable IEC and IEEE standards
Stainless steel resistor elements
Excellent high voltage strength
Low inductance resistor elements for easy tuning
Large variety of harmonic filters for optimum solution
Stainless steel, hot dip galvanized steel or aluminium resistor enclosures on demand
Corrosion and heat resistant electrostatic paint for indoor and outdoor applications
Compact design
Elevation stands are available
Cooling fans are available on demand
Insulators with high creepage distance are provided on demand for highly polluted areas
and high altitudes
Current Limiting Resistors
Power Resistors
Areas of Usage
High Power Test Laboratories Motor Starting Electric Arc Furnaces Induction
Furnaces
Features

Stainless steel grid

Stainless steel grid elements

Typically 2 mm hot dip galvanised steel enclosure on demand

High thermal capacity to absorb high currents

Rugged-shock resistant construction

High altitude ratings

Corrosion resistant nameplate

Specially designed units for hazardous and extreme locations

Designed and tested to applicable IEC and IEEE standards
Installation
The dimensions of the resistor can be adjusted to customer specific needs in
order to meet unusual space requirements.
Complete installation guidelines are provided with the resistors in order to
meet required clearances. Each resistor is supplied with installation
guidelines that specifies step by step methods for installation.
Support Stands
Aluminum, hot dip galvanised steel or concrete support stands are designed
for specific applications.
Quality Assurance
Hillkar maintains a complete quality assurance program including ISO 9001
and other European and American Standards in manufacturing plant.
Technical Support
Hillkar provides complete technical assistance to contractors and end
customers for applications, design, calculations and field installation. All
Hillkar resistors are custom designed for different applications by considering
the voltage, current, inductance, size, loss characteristics that are required to
provide the most efficient design at the most economical prices.
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RC Filters
Power Resistors
Areas of Usage
RC Filter components are made of low inductance resistors and capacitors in order to
protect M.V. motors, generators and dry type transformers, and shunt reactors against
very fast transient and over voltages. R - C snubber filters are connected in parallel
between motors, generators etc. and switchgears.
Advantages:

Longer insulation lifetime for machinery

Protects against insulation failures between windings

Protects against re-ignitions between the contacts of vacuum circuit breakers and
other switchgear due to high frequency over voltage

Protects against high frequency over voltage specifically caused by arc furnaces

Optional earth fault relay by arc furnaces
Up to 36kV High Frequency
Transient Surge
Suppression RD Filter
Application Areas:
Large motors, generators, induction and arc furnaces, shunt reactors, dry type
transformers.
With R-C filter during Switching
With R-C filter during Switching
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Without R-C filter during Switching
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Product Overview (1kV to 500kV)
 Fault Circuit Indicators
 HV Circuit Breakers
 Reactive-Power Compensation
 Power Factor Correction
 Indoor AIS and Vacuum Components
 Integrated Voltage Detecting Systems
 Insulators and Line Hardware
Accessories
 Motor Operating Devices
 AIS Switches and Disconnectors
 Power Resistors
 Ripple Control Systems
 Solvents and Lubricants
 Surge Protection
 Fuses and Fuse Tester Devices.
 HV Testers and Testing Sticks
Services
 Consultancy Services
 Local Repair /Modernisation Facility
 Installation Supervision
“Flexibility in providing solutions to exceed our
customers’ needs through reliability and service.”
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CUSTOMER SERVICE & SUPPORT
Ph: +61 (0) 2 9726 7702
Fax: +61 (0) 2 9726 7703
[email protected]
Subject to change without prior notice. The information in this document contains general descriptions of the technical options available,
which may not apply in all cases. The required technical options should therefore be specified in the contract.

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