Most failures of electrical power equipment result from a breakdown in the insulation system. To minimize failures, it is recommended to conduct periodic maintenance testing of the insulation to determine its rate of deterioration.
Hengfeng contains other products and information you need, so please check it out.
Power factor tests are employed to measure dielectric losses, which are indicative of the wetness, dryness, or deterioration of electrical insulation.
Power factor is defined as the cosine of the phase angle between voltage and current. In an ideal insulation scenario, the phase angle is 90°. However, in practice, no insulation is ideal; each has a certain amount of loss, and the total current leads the voltage by a phase angle less than 90°.
Measuring insulation power factor is achieved by calculating the ratio of the capacitive or “charging” current (measured in volt-amperes) to the resistive or “leakage” current (measured in watts).
Vector Components of Power Factor Test Voltage and Current
Testing power factor is a means of measuring the integrity of the insulation. The smaller the power factor, the better the insulator, making this one of the best testing techniques for predictive and preventive maintenance.
Power factor testing enables the detection of equipment insulation problems without the need for internal visual inspection. The result is a significant decrease in maintenance costs and downtime.
The power factor test set utilizes an AC voltage and comes with three basic modes of operation:
GST - Grounded Specimen Test
GST Guard Mode - Guarded Specimen Test
UST - Ungrounded Specimen Test
When considering the three different modes of operation, it is important to understand which test leads are associated with each mode. Power factor test sets have four leads for connecting to the device under test:
Power factor test sets have four different leads for connecting to the device under test. Photo: TestGuy
High Voltage Output Lead - Supplies the voltage necessary to produce the test current. Not specific to any mode of operation. Power factor testing is typically performed at 10 kV, or values equivalent to 10 kV are obtained.
Ground Return Lead (GST) - Measures current flowing through the ground path.
Red/Blue Leads (UST) - Used to guard out current not flowing through the ground path. Examples of this include the leakage between the high-side winding and low-side winding of a transformer or the current leaking between the line side and the load side of an open circuit breaker. Of the two UST leads, only one is actually used in over 95% of practical applications.
When you break it all down, it’s quite simple: There are two paths of leakage current returning to the test set—ground or guard.
When considering the three different modes of the power factor test set, it is important to understand which test leads are associated with each mode. Photo: Doble.
The GST Guard test measures the total current leaking to ground only. The power factor test set ignores current flowing through the red or blue lead.
Conversely, in UST mode, ground is considered guard since grounded terminals are not measured. During the UST test, the only current being measured by the test set is the current flowing on the red or blue lead. Any current flowing to a grounded terminal is bypassed directly to the AC source return and is eliminated from the measurement.
UST mode is used to measure insulation between two ungrounded terminals of the apparatus, isolating an individual section of insulation for testing without measuring other connected insulation.
In the last mode of operation, the GST mode, both leakage paths (ground lead and the red or blue lead) are measured by the test set. The current, watts loss, and capacitance parameters of the UST and GST Guard tests should equal the parameters in the GST test. This provides the overall condition or power factor of the test specimen.
If the sum of the UST and GST guarded parameters does not equal the GST parameters, then either the test set is malfunctioning, or the test leads are configured incorrectly.
Beer is active power (kW)—the useful power, or the liquid beer, is the energy that is doing work. This is the part you want.
Foam is reactive power (kVAR)—the foam is wasted power or lost power. It’s the energy being produced that isn't doing any work, such as the production of heat or vibration.
Are you interested in learning more about power factor tester? Contact us today to secure an expert consultation!
The mug is apparent power (kVA)—the mug is the demand power, or the power being delivered by the utility.
If a circuit were 100% efficient, demand would be equal to the power available. When demand is greater than the power available, a strain is placed on the utility system. Many utilities add a demand charge to the bills of large customers to offset differences between supply and demand (where supply is lower than demand). For most utilities, demand is calculated based on the average load placed within 15 to 30 minutes. If demand requirements are irregular, the utility must have more reserve capacity available than if load requirements remain constant.
Peak demand is when demand is at its highest. The challenge for utilities is delivering power to handle every customer’s peaks. Using power at the very moment it is in highest demand can disrupt overall supply unless there are enough reserves. Therefore, utilities bill for peak demand. For some larger customers, utilities might even take the largest peak and apply it across the full billing period.
Utilities apply surcharges to companies with a lower power factor. The costs of lower efficiency can be steep—akin to driving a gas-guzzling car. The lower the power factor, the less efficient the circuit, and the higher the overall operating cost. The higher the operating cost, the higher the likelihood that utilities will penalize a customer for overutilization. In most ac circuits there is never power factor equal to one because there is always some impedance (interference) on the power lines.
To calculate power factor, you need a power quality analyzer or power analyzer that measures both working power (kW) and apparent power (kVA), and to calculate the ratio of kW/kVA.
The power factor formula can be expressed in other ways:
PF = (True power)/(Apparent power)
OR
PF = W/VA
Where watts measure useful power while VA measures supplied power. The ratio of the two is essentially useful power to supplied power, or:
As this diagram demonstrates, power factor compares the real power being consumed to the apparent power, or demand of the load. The power available to perform work is called real power. You can avoid power factor penalties by correcting for power factor.
Poor power factor means that you’re using power inefficiently. This matters to companies because it can result in:
Heat damage to insulation and other circuit components
Reduction in the amount of available useful power
A required increase in conductor and equipment sizes
Finally, power factor increases the overall cost of a power distribution system because the lower power factor requires a higher current to supply the loads.
Whether you operate a casino, aviation center, power plant or oil facility, electrical power equipment can fail—no matter what your facility may be! Often, these failures occur because the insulation system is damaged, and regularly scheduling a power factor test can prevent them from happening. Not only can this test detect if there’s deterioration within the equipment, but through it will also tell you how quickly the deterioration is occurring by performing routine testing. Not sure what a power factor test is?
Power factor tests are able to detect deterioration in electrical equipment because their sole purpose is to calculate dielectric losses. What this means is: if there is wetness, dryness or deterioration present in electrical insulation, this test will detect it and calculate its severity.
In a perfect world, insulation measures at an angle of 90°. However, no electrical insulation is perfect, and therefore, most have an angle that measures slightly under 90°. To obtain this measurement, calculate the ratio of the volt amperes (the “charging” current) with the watts (“leakage” current). A power factor test is one of the best methods for predictive and preventative maintenance because it is able to calculate the health of the insulation. Additionally, this method of testing enables the technician to pinpoint insulation issues without having to visually inspect the interior of the electrical equipment, meaning less cost and downtime for a facility.
The power factor test is so effective because it uses AC voltage from three different types of operation. These are:
GST Guard: This voltage only calculates current that leaks to the ground, and the power factor test does not take note of current that flows through either the red or blue measurement leads.
UST: Unlike with the GST Guard Test, this one only calculates the current that is flowing through the red and blue measurement leads—anything that flows through ground is ignored.
GST Mode: This operation calculates the insulation between two ungrounded terminals of the equipment. It does so by isolating an area of insulation and testing it while ignoring other insulation that is connected.
Eventually, we'll need a few more details to facilitate your rental/finance, but we know your time is valuable.
Do you want to submit the request now, or do you have some time to enter company details?
If you are looking for more details, kindly visit DC hipot tester.