![Schweitzer Engineering Laboratories SEL-421-4 Скачать руководство пользователя страница 1028](http://html.mh-extra.com/html/schweitzer-engineering-laboratories/sel-421-4/sel-421-4_instruction-manual_12167261028.webp)
7.4
SEL-400 Series Relays
Instruction Manual
Date Code 20171006
Metering
Instantaneous Metering
Table 7.3
Instantaneous Metering Accuracy—Power
Quantity
Description
Power Factor
Accuracy (%)
a
a
Power accuracy is valid for applied currents in the range (0.1–1.2) • I
NOM
, and applied voltages
from 33.5–75 V.
At 0.1 • I
NOM
3P
Three-phase rms real power
Unity
±0.40
–0.5 or +0.5
±0.70
3Q
1
Reactive power
–0.5 or +0.5
±0.50
At 1.0 • I
NOM
3P
Three-phase fundamental real power
Unity
±0.40
–0.5 or +0.5
±0.40
3Q
1
Reactive power
–0.5 or +0.5
±0.40
Example 7.1
Calculating Exact Error Coefficients
Consider the case of a 5 A relay during normal operating conditions. The
secondary current in the CT is 1.0 A for nominal system operation. Noting
that this current is greater than 10 percent of I
NOM
(1 A > 0.5 A), calculate
the error coefficient:
error = ±(0.2% • 1.0 A) ± (0.8 mA • I
NOM
)
= ±(0.002 • 1.0 A) ± (0.0008 A • 5)
= ±(0.002A ± 0.004A)
= +0.002 A to +0.006 A
and
= –0.006 A to –0.002 A
Equation 7.1
represents the calculated accuracy range. The error is very small,
indicating that the relay measures normal operating currents accurately.
Figure 7.2
Typical Current Measuring Accuracy
Measured Current (A)
0.994
0.998
1.006
1.002
0
1.0
1.0
I
NOM
= 5 A
Actual Value
Содержание SEL-421-4
Страница 6: ...This page intentionally left blank ...
Страница 14: ...This page intentionally left blank ...
Страница 30: ...This page intentionally left blank ...
Страница 104: ...This page intentionally left blank ...
Страница 128: ...This page intentionally left blank ...
Страница 536: ...This page intentionally left blank ...
Страница 584: ...This page intentionally left blank ...
Страница 616: ...This page intentionally left blank ...
Страница 696: ...This page intentionally left blank ...
Страница 750: ...This page intentionally left blank ...
Страница 755: ...Instruction Manual PM400 01 NB SEL 400 Series Relays Instruction Manual 20171006 ...
Страница 776: ...This page intentionally left blank ...
Страница 932: ...This page intentionally left blank ...
Страница 976: ...This page intentionally left blank ...
Страница 1024: ...This page intentionally left blank ...
Страница 1038: ...This page intentionally left blank ...
Страница 1064: ...This page intentionally left blank ...
Страница 1128: ...This page intentionally left blank ...
Страница 1206: ...This page intentionally left blank ...
Страница 1316: ...This page intentionally left blank ...
Страница 1350: ...This page intentionally left blank ...
Страница 1464: ...This page intentionally left blank ...
Страница 1468: ...This page intentionally left blank ...
Страница 1492: ...This page intentionally left blank ...
Страница 1518: ...This page intentionally left blank ...