IEEE Std 1137 pdf free download
IEEE Std 1137 pdf free download.Implementation of Inductive Coordination Mitigation Techniques and Application.
4.1.1 Influence
Influence refers to the capability of a power circuit to cause interference in a nearby communication circuit. Unbalanced phase currents, excessive earth return currents, and distorted voltage or current wave shapes contribute to high influence. The power utility and its users jointly control or affect influence. A measure of the influence of a power line is obtained by either utility, through measurements on a probe wire interface placed near and parallel to the power line. Refer to IEEE Std 776.
NOTE—The term power influence (Pt) introduced in 4.2.1 has a completely different meaning from this traditional concept of the influence of a power system.5
4.1.2 Coupling
Coupling refers to the mutual impedance between the power and communication lines (see Sunde [85j and Carson [B2]).6 Magnetic (inductive) coupling and electric (capacitive) coupling depend upon length of exposure, earth resistivity, frequency. separation, and shielding. Mutual impedance is computed by using equations as found in IEEE Std 367TM.
Conductive (resistive) coupling depends upon the size and proximity of ground electrodes of the two systems, as well as on earth resistivity, frequency, and upon the presence or absence of metallic connections between grounded parts of the two systems (and upon the resistance or impedance of such bonds, if present).
4.1.3 Susceptiveness
Susceptiveness (or susceptibility) refers to those characteristics that determine the extent to which the service rendered by a communications circuit can be adversely affected by a given longitudinal voltage or current. Susceptiveness can be expressed in terms of relationships between the longitudinal voltage or current and the resulting metallic voltage or current (balance). Alternatively, susceptiveness can be expressed as the limiting voltage or current that a device or system can withstand without malfunction or damage. The communication utility and its users jointly control the susceptiveness of the communication circuit: Refer to IEEE Std 776. It should be noted that susceptiveness is frequency dependent.
4.2 Communication noise investigation
4.2.1 Preliminary measurements
Communication lines are, in general, reasonably quiet and free from audible interference. Noise investigations usually only take place upon receipt of a customer complaint. A technician would be dispatched to investigate the complaint. Standard equipment is commercially available for the technician to make the following tests from the network interface (NI):
a) Loop current. The tester should measure and record the milliamperes of direct current flowing through the loop and a 430 resistor with the customer equipment in the on-hook condition. This measured current should be 20 mA or more. Refer to IEEE Std 820TM.
b) Circuit loss. The tester should USC a test handset to dial up the office milliwatt. This results in a transmission of a 1004 Hz tone from a 0 dBm supply (1 mW) from the ccntral office (CO). The measuring set in the bcircuit loss” setting measures the received level as a negative dBm value. This value should be recorded by the tester. The reading should not be less (more negative) than —10 dBm. This would represent a circuit loss of 10 dB, which should not be exceeded for good communication transmission. Refer to IEEE Std 820.
c) Circuit noise. Many test milliwatis automatically switch to a quiet line termination after a short period of time. If this does not happen, the tester should dial a separate Quiet Line number to obtain a grounded balanced termination at the CO. The test set, with the circuit noise setting, would read C Message Weighted Metallic Noise in dBrnC. The tester should record this reading.
d) Power influence (P1), also called C message weighted longitudinal noise or C message weighted noise- to-ground. See Equation 1). (Note that some noise measuring sets (NMS) need a 40 dli correction to bc added to the reading to obtain Pt. But the test sets generally available to the technician usually measure P1 directly in dBrnC.) This reading should be recorded.
c) The tester should calculate and record the longitudinal balance from the measured P1 and Circuit noise by taking the difference (in dB) between the P1 reading and the circuit noise reading.
For the purpose ofeomparing unweighted to weighted values, measure the rms ac voltage across a 100 000 resistor from the circuit to ground. Convert the voltage reading to an unweighted dIim reading and compare to the C message noise-to-ground reading in dlirnC. Refer to IEEE Std 776.IEEE Std 1137 pdf download.
