18-013-909 Positive angles indicate that the “next” phase lags this phase (see Figure 10). A negative Voltage Multiplier (see AV1142) for one phase rotates the result by 180°, also normalized. (Negative multipliers on both phases cancel each other) This measurement assumes that both phases have the same frequency (the meter does not check). If the voltage of either phase drops too low, this value returns 0 V. With a PowerPrint Voltage Angle target set (see AV1146), angle variations may set the Phase Drift condition (see AV400). If so, Reliability will return Over Range or Under Range, as appropriate. Otherwise, Reliability always returns some combination of the two phase reliabilities. With no PowerPrint Voltage Angle target, the meter substitutes 120°, a standard angle for 3-phase services. Three angles of approximately –120° will set the Reverse RST Order condition. Three angles not approximately equal to either –120° or +120° will set the Not Three Phase condition. Phase Loss on either phase blocks both conditions from being set. The default smoothed value response time is 60 seconds (see AV142). AI1442 Smoothed ● AI1444 Minimum ● AI1446 Maximum ● AI1448 Average AI1450 R to S Phase RMS Voltage R/W0 Returns the RMS voltage 𝑽𝑷𝑷 between the “hot” leads of this phase and the next (as defined by AI1440), in V. This calculation assumes a common neutral connection (see Figure 11) between phases and that both phases have the same frequency (the meter does not check for either). V1 V2 VPP θ CVT 2 CVT 1 Figure 11: Phase to Phase Common Neutral The following equation represents the basic phase to phase voltage calculation: 𝑽𝑷𝑷 = �(𝑽𝟏 − 𝑽𝟐 𝐜𝐨𝐬 𝜽)𝟐 + (𝑽𝟐 𝐬𝐢𝐧 𝜽)𝟐 A negative Voltage Multiplier (see AV1142) for exactly one phase rotates the result by 180°, effectively reversing the polarity of the neutral and “hot” leads. Reliability always returns some combination of the phase and angle reliabilities. The default smoothed value response time is 10 seconds (see AV144). AI1452 Smoothed ● AI1454 Minimum ● AI1456 Maximum ● AI1458 Average Figure 10: Phase Progression R S time θ τ = 360° EM-RS485 BACnet Protocol Guide Page 23 of 49 154-0022-0C AI1520 RMS Current R/W0 Returns the effective line RMS current 𝑰 measured with the CVT current sensing loop and multiplied by the Current Multiplier (see AV1152), in A. Always positive, regardless of the sign of the multiplier. When the current exceeds the Current Rating (see AV1150) the measurement may have a reduced accuracy, and Reliability may return Over Range. Fundamentally, Rogowski coils measure changes in current, not current itself. This is why Rogowski coils are not well-suited for DC current measurements and also why they may be sensitive to high frequency harmonics. Even though a particular RMS current may be within the CVT Current Rating, individual harmonic components may exceed the input range. If the meter detects that current harmonics may lead to reduced accuracy, the High Harmonics condition (see AV1400) will be set. However, given the wide variation in harmonics between different loads, the meter cannot detect every possible scenario leading to reduced accuracy. The default smoothed value response time is 2 seconds (see AV154). AI1522 Smoothed ● AI1524 Minimum ● AI1526 Maximum ● AI1528 Average AI1540 Current Angle R/W0 Returns the four quadrant current angle 𝝋. The default units are Degrees (see MSV153), normalized between –180 and +180°. A negative Current Multiplier (see AV1152) rotates the result by 180°, effectively reversing the orientation of the current sensor loop. Current angle measures the angle of the phase current fundamental with respect to the voltage fundamental. Positive angles represent leading (capacitive) loads. Internally, the meter calculates from the vector formed by Real Power (see AI1600) and Reactive Power (see AI1640). Note the negation required to maintain sign convention (see Figure 12): 𝝋 = −atan 𝑸 𝑷 Displacement power factor may be easily derived from current angle: 𝒑𝒇𝑫 = cos(𝝋) = 1 �1 + � 𝑸 𝑷� 2 During No Load conditions the Real Power (see AI1600) becomes too small for reliable calculation. In this case Present Value returns 0° and Reliability returns Under Range. Otherwise, Reliability returns some combination of the RMS Voltage and RMS Current reliabilities. The default smoothed value response time is 2 seconds (see AV154). AI1542 Smoothed ● AI1544 Minimum ● AI1546 Maximum ● AI1548 Average +Reactive Import Lagging Import Leading Export Lagging Export Leading –Reactive –Real +Real Q P -φ V I Figure 12: Current Angle Quadrants EM-RS485 BACnet Protocol Guide Page 24 of 49 154-0022-0C AI1550 Power Factor R/W0 Returns true (a.k.a. apparent) power factor 𝒑𝒇. A negative value indicates export power. 𝒑𝒇 = 𝑷 𝑺� = 𝑷 𝑽 ∙ 𝑰 � Reliability follows Current Angle (see AI1540), including No Load conditions (see AI1600). When power factor drops below 0.5 (absolute value), the Low Power Factor condition (see AV1400) is set. Low Power Factor may indicate an installation error (see Installation Instructions). The default smoothed value response time is 2 seconds (see AV154). AI1552 Smoothed ● AI1554 Minimum ● AI1556 Maximum ● AI1558 Average AI1600 Real Power R/W0 Returns real power 𝑷, after multiplication by the Power Multiplier (see AV1162). The default units are kW (see MSV163). A negative value indicates export power. When Real Power drops very low, the No Load condition (see AV1400) is set. During No Load conditions, Current Angle (see AI1540) and Power Factor (see AI1550) measurements become unreliable. The No Load condition is also set during Phase Loss conditions. The Import and Export Averages only update during the respective intervals (see Figure 13). The Import Average is always positive, and the Export Average is always negative. When power flows exclusively in one direction, one of these will remain at 0 kW. Maximum Import Average Overall Average Minimum Export Average Figure 13: Real Power Averages During Phase Loss conditions (see AI1420), returns 0 kW, all of the Averages stop updating, and Reliability returns Under Range. Otherwise, Reliability returns a combination of RMS Voltage and RMS Current reliabilities. The default smoothed value response time is 2 seconds (see AV164). AI1602 Smoothed ● AI1604 Minimum ● AI1606 Maximum AI1608 Overall Average ● AI1610 Import Average ● AI1612 Export Average AI1640 Reactive Power R/W0 Returns reactive power 𝑸, after multiplication by the Power Multiplier (see AV1162). The default units are kVAR (see MSV163). A negative value indicates a capacitive load (leading power factor). The Import and Export Averages only update during the respective Real Power (see AI1600) intervals. When Real Power flows exclusively in one direction, one of these will remain at 0 kW. All three averages may be positive or negative, depending on the mix of capacitive and inductive loads. During Phase Loss conditions (see AI1420), returns 0 kVAR, all of the Averages stop updating, and Reliability returns Under Range. Otherwise, Reliability follows Real Powe |
