Sel SEL-421 - Time Error Command; Time-Error Calculation Inputs and Outputs; Sample TEC Command Response

R.1.17
Date Code 20111215 Reference Manual SEL-421 Relay
Protection Functions
Time-Error Calculation
Tab le 1.14 lists the inputs and outputs of the time-error function.
Time Error Command
(TEC)
The TEC serial port command provides easy access to the time-error function.
See TEC on page R.9.51 for command access level information.
Enter the TEC command to view the time-error status. A sample display is
given in Figure 1.13.
=>TEC <Enter>
Relay 1 Date: 11/02/2004 Time: 11:25:50.460
Station A Serial Number: 0000000000
Time Error Correction Preload Value
TECORR = 0.000 s
Relay Word Elements
LOADTE = 0, STALLTE = 0, FREQOK = 1
Accumulated Time Error
TE = -7.838 s
=>
Figure 1.13 Sample TEC Command Response
Enter the TEC command with a single numeric argument n (–30.000  n 
30.000) to preload the TECORR value. This operation does not affect the TE
analog quantity until the SEL
OGIC control equation LOADTE next asserts.
Figure 1.14 shows an example of the TEC n command in use.
Table 1.14 Time-Error Calculation Inputs and Outputs
INPUTS Description
Analog Quantities
FREQ Measured system frequency (see Table 1.13).
TECORR Time-error correction factor. This value can be preloaded
via the TEC command, or DNP3.
Global Settings
NFREQ Nominal frequency (see Table 10.3 on page R.10.5)
LOADTE Load Time-Error Correction Factor (SEL
OGIC control equa-
tion). A rising edge will cause the relay to load the
TECORR analog quantity into TE. LOADTE has priority
over STALLTE.
STALLTE Stall Time-Error Calculation (SEL
OGIC control equation). A
logical 1 will stall (freeze) the time-error function. The TE
value will not change when STALLTE is asserted (unless
LOADTE asserts).
Relay Word bit
FREQOK Frequency Measurement valid. If this Relay Word bit deas-
serts, the TE quantity is frozen (see Table 1.13).
OUTPUTS Description
Analog Quantity
TE Time-Error estimate, in seconds. Positive numbers indicate
that the ac clock would be fast (ahead of the reference
clock). Negative numbers indicate that the ac clock would
be slow (behind the reference clock).
Relay Word bit
PLDTE Preload Time-Error value updated. This element asserts for
approximately 1.5 cycles after TECORR is changed by the
TEC command or by DNP3.