Transmission Line/Station Testing

Transmission Line/Station Testing

Transmission Line/Station Testing devices are used to measure and test a variety of parameters as well complete various job tasks on Transmission Lines and Substations. They make the user’s job easier, safer, and more efficient. Transmission Line/Station Testing devices come in a variety of styles and sizes to meet a range of needs.
 
Transmission Line/Station Testing Applications

• Measure current flow on overhead line systems
• Confirm the presence of dangerous high voltage
• For use on grounded and ungrounded systems
• For field or shop use
• Phase angle comparison and indication of phase angle voltage at the point of intended paralleling of two circuits
• Monitor quality of transformer insulating oils

Types of Transmission Line/Station Testing

High Current Detectors/Indicators

High Current Detectors/Indicators are used to measure current flow on overhead line systems. These digital devices provide a RMS reading. The sensing unit is fully screened against the effects of electrostatic fields.
 
High Current Detectors/Indicators Application
 
Measure current flow on overhead line systems
 
Key Features of High Current Detectors/Indicators to Consider

• True RMS reading
• Amperage Range
• Max Voltage
• Accuracy

High Voltage Detectors/Indicators

High Voltage Detectors/Indicators are used to detect the presence of voltage on any grounded and neutral electrical system. They can also be used as a voltmeter. They are designed to meet safety standards and come in a variety of styles and sizes to meet a range of needs.
 
High Voltage Detectors/Indicators Applications

• For use on any grounded electrical system
• For use on distribution line voltages
• Use as a potential indicator to determine presence of voltage or as a voltmeter
• Confirm the presence of voltage on earthed neutral electrical systems

Key Features of High Voltage Detectors/Indicators

• Continuous Monitoring
• IEC conformance
• No switches
• Provides direct reading of voltage measurements
• Permanently connected earth cable
• Duplicate neon indicators within shock resistant sleeves
• Direct access to vertical or horizontal metal clad switch gear
• Hand guards on all elements

High Current and Circuit Breaker Testers

High Current and Circuit Breaker Testers combine a variable high current output with the appropriate controls and instrumentation. The test set is ideal for testing thermal, magnetic, and solid-state motor overload relays as well as molded-case circuit breakers and ground fault trip devices. They can also be used in many other applications requiring a high current source.
 
High Current and Circuit Breaker Testers Applications

• For field or shop use
• Economical and portable primary injection testing
• Test virtually any low voltage, molded case, or metal clad direct acting AC circuit breaker by simulating overload and fault conditions
• Test current transformers and thermal or magnetic motor overload relays
• Substation maintenance

Types of High Current and Circuit Breaker Testers

• Circuit Breaker Testers
• High Current Test Sets

Key Features of High Current and Circuit Breaker Testers to Consider

• Built for field or shop use
• Provides a short duration output of 1000 amps through a typical 150 ampere molded-case circuit breaker when an instantaneous trip element must be tested
• Unique auto-sensing
• When the output is initiated the pre-set output current locks on and the timer starts
• When the test set senses a change in state of the test object (NO to NC or NC to NO), the current shuts off and the timer stops
• Memory feature of the current meter holds the peak current value until reset by operator
• Windows based software
• Computerized controls with user-friendly, menu-driven commands

Hot Sticks

Hot sticks are used to protect users from electric shock. They are insulated poles and are used to perform functions such as testing voltage, tightening nuts and bolts, open and close switches, and a variety of other tasks. They are typically used by utility workers working on live lines.

Phasing Sticks

Phasing sticks provide a means of phase comparison at the point of paralleling two circuits, without the interposition of voltage transformers or secondary wiring circuits. Models are available for both grounded and ungrounded systems.
 
Phasing Sticks Applications

• Phase angle comparison and indication of phase angle voltage at the point of intended paralleling of two circuits on neutral earthed systems
• Grounded or ungrounded AC system check
• Outdoor testing of grounded and ungrounded systems
• Use on 1kV to 11.5kV systems

Types of Phasing Sticks

• Analog
• Digital

Key Features of Phasing Sticks

• Bright LED indication
• PVC hand guards on handles of elements
• Neon indicator enclosed in shock resistant sleeve
• Direct areas possible to all types of switch gear

Transmission Cable Height Meters

Cable Height Meters are used in the measurement of cable height, cable sag (lowest point to ground) and overhead clearance.

Ultrasonic Distance Meters are terrific and affordable alternatives to a tape measure for distance measurements. They offer the convenience of being able to make measurements without a second person to hold the measuring tape. Easily measure hard-to-access areas, like high ceilings or depths such as an elevator shaft or well, without climbing a ladder. The instrument can be used to ensure that OSHA overhead clearance regulations are met at construction sites. It also provides a safer way to measure cable heights on highly congested roadways.

General tips when using distance meters

• Always measure perpendicular to the target. Do not point at an angle
• Speed of sound increases with higher temperature and to a small extent speed increases at higher humidity. Ultrasonic distance meters compensate for temperature by including an ambient temperature sensor. Ultrasonics have a beam angle. Best analogy is a flashlight pointed at a wall. The cone increases and decreases as one moves away or comes closer. When using ultrasonics for long distances care must be taken not to have objects within the operating beam angle.

How does a distance meter work?

Distance meters operate on the principle of time of flight. Ultrasonic distance meters will excite a piezo crystal with high voltage low amperage to create a sound pulse in the kHz range. The time taken for the pulse to make a round trip to the target is measured. The speed of sound is known and so the distance can be calculated. Similarly laser distance meters send a pulse of light, however light pulses are much faster requiring high speed timers.

Dielectric Oil Testing

Physical properties of insulating oils are important to monitor. Various laboratory test instruments are available to meet the different test methods.

Oil dielectric strength test set is one such test. Excerpt from ASTM D1816 Test Method: The oil dielectric strength test instrument carried by TEquipment is suitable for field use and can be powered from a range of mains supplies. The maximum 60 kV output allows tests to be performed on oil from a wide variety of electrical installations including transformers, circuit breakers and other equipment. The operation of the test set is extremely simple and the results are displayed on a bright LED display. A selection of vessels allows the instrument to be configured for a variety of test standards.

The microprocessor controlled, semi-automatic operation allows the user to select a choice of voltage rise rates as specified in many national standards. The start button will then initiate the test. If oil breakdown occurs the instrument will remove the test voltage and display the breakdown value. Alternatively the user can pause the test voltage at any time to carry out a withstand test. The voltage will be maintained at this level for one minute or until breakdown. After one minute the voltage will automatically continue to rise until breakdown occurs or to the maximum output of the instrument.

Over the years various U.S. and International Standards have been developed for oil dielectric strength.  While the instrument may perform multiple tests, test procedure and accessory glassware varies by test. With any order specify the test method(s), so proper glassware can be recommended.
 

List of Domestic and International Oil Dielectric Strength Test Methods

Test Method	Title
ASTM D877	Standard Test Method for Dielectric Breakdown Voltage of Insulating Liquids Using Disk Electrodes
ASTM D1816	Standard Test Method for Dielectric Breakdown Voltage of Insulating Liquids Using VDE Electrodes
IEC 156	Test Method for Dielectric Breakdown Voltage of Insulating Oils
VDE 370 (German)	Test Method for Dielectric Breakdown Voltage of Insulating Oils

Excerpt from ASTM D877
This test method describes two procedures, A and B, for determining the electrical breakdown voltage of insulating liquid specimens. The breakdown test uses ac voltage in the power-frequency range from 45 to 65 Hz. This test method is used to judge if the disk electrode breakdown voltage requirements are met for insulating liquids, as delivered from the manufacturer, that have never been filtered or dried.

Excerpt from ASTM D1816
This test method covers the determination of the dielectric breakdown voltage of insulating liquids (oils of petroleum origin, silicone fluids, high fire-point mineral electrical insulating oils, synthetic ester fluids and natural ester fluids). This test method is applicable to insulating liquids commonly used in cables, transformers, oil circuit breakers, and similar apparatus as an insulating and cooling medium.