Measurement power factors

Power factor adjustment Although related to the average power factor of the load, the method of calculation may be based directly on measured power factor or on the measurement of reactive kVA over the period. Values at which power factor charges are incurred vary from 0.8 to 0.95 lag. 

Typical power factors for an EPR-based compound employed for 5—35 kV power cable is approximately 0.03—0.05% when measured at room temperature and about 1.0—1.4% measured at 90°C. 

The power factor of polyethylene which provides the measure of the power loss in the insulated conductor increases slightly with an increase in the temperature of the atmosphere or the electrical equipment, both of which may fluctuate widely. It also increases slightly with an increase in the humidity of the surroundings. 

In the second method, the pump and the motor are coupled direcdy, and either power (in kilowatts) or the current, I, and voltage, U, ate measured at the motor terminals. To determine the power actually transmitted into a pump, the motor power factor (PF) and efficiency (Eff ) must be known. These values ate usually taken from the motor manufacturer s caUbration curves (17). 

They are used for botli measuring and protection purposes. As a measuring VT, they are used to feed a voltmeter, kW, kWh or a kVAr meter, a power factor, frequency meter or a synchroscope. As a protection VT they are used to feed a protective circuit, incorporating voltage sensitig protection relays. To save on cost and mounting... 

These are employed for the measurement of power circuit currents through an ammeter, kW, kWh or KVAr and power factor meter, or similar instruments requiring a current measurement. They must have a specified accuracy class as in lEC 60044-1 and the secondary current substantially proportional to the primary within a working range of about 5-120% of its primary rated current. They... 

Guide for methods of power factor measurement for LV inductive lest circuits... 

A true RMS wattmeter for conveniently measuring efficiency and power factor. This is needed for off-line power supplies. 

The chemical resistance of polyethylene is, to a large measure, that expected of an alkane. It is not chemically attacked by non-oxidising acids, alkalis and many aqueous solutions. Nitric acid oxidises the polymer, leading to a rise in power factor and to a deterioration in mechanical properties. As with the simple alkanes, halogens combine with the hydrocarbon by means of substitution mechanisms. 

PTFE is an outstanding insulator over a wide range of temperature and frequency. The volume resistivity (100s value) exceeds lO Gm and it appears that any current measured is a polarisation current rather than a conduction current. The power factor is negligible in the temperature range -60°C to -i-250°C at frequencies up to lO" Flz. The polymer has a low dielectric constant similarly unaffected by frequency. The only effect of temperature is to alter the density which has been found to influence the dielectric constant according to the relationship... 

Efficiency at full, and V2 load Power factor at full, and V2 load Winding resistance measurement Bearing inspection... 

It should be noted that this is not necessarily the actual instantaneous maximum demand. The quantity measured on this meter is, of course, the maximum kW demand, but some forms of tariff are based on the maximum kVA demand in order to encourage power factor improvement (see below). 

The loss factor is the product of the dielectric constant and the power factor, and is a measure of total losses in the dielectric material. 

Methods for measuring the resistivity of insulating materials are based on IEC 60093 [24] and insulation resistance is covered by IEC 60167 [25]. For conducting and antistatic materials the methods for rubbers, ISO 1853 [26] for resistivity and ISO 2878 [27] for resistance, could be adapted and there is a draft IEC standard. The general method for electric strength is IEC 60243 [28] and methods for power factor and permittivity are often based on IEC 60250 [29]. 

Material response is typically studied using either direct (constant) applied voltage (DC) or alternating applied voltage (AC). The AC response as a function of frequency is characteristic of a material. In the future, such electric spectra may be used as a product identification tool, much like IR spectroscopy. Factors such as current strength, duration of measurement, specimen shape, temperature, and applied pressure affect the electric responses of materials. The response may be delayed because of a number of factors including the interaction between polymer chains, the presence within the chain of specific molecular groupings, and effects related to interactions in the specific atoms themselves. A number of properties, such as relaxation time, power loss, dissipation factor, and power factor are measures of this lag. The movement of dipoles (related to the dipole polarization (P) within a polymer can be divided into two types an orientation polarization (P ) and a dislocation or induced polarization. 

The power factor is the energy required for the rotation of the dipoles of a polymer in an applied electrostatic field of increasing frequency. Typical values vary from 1.5 x 10 for polystyrene to 5 x 10 for plasticized cellulose acetate. Values increase at Tg and because of the increased chain mobility gained so that Tg and Tm have been measured using differences in the power factor as temperature is increased. 

The electric properties of a material vary with the frequency of the applied current. The response of a polymer to an applied current is delayed because of a number of factors including the interaction between polymer chains, the presence within the chain of specific molecular groupings, and effects related to interactions within the specific atoms themselves. A number of parameters are employed as measures of this lag, such as relaxation time, power loss, dissipation factor, and power factor. 

---