Applying The Function Parameter Settings - Siemens SIPROTEC 7SA6 Manual

Distance protection relay for all voltage levels

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>BLK ThOverload

Figure 6-138Logic diagram of the thermal overload protection

6.19.2 Applying the Function Parameter Settings

General Informa-

4203 TIME CONSTANT

4202 K–FACTOR

4205 I ALARM

A precondition for the use of the thermal overload protection is that Overload =

Enabled was configured under address 142 (Section 5.1). It can be switched On or

Off under address 4201 Ther. OVERLOAD . Furthermore Alarm Only can be set.

With that latter setting the protection function is active but only outputs an alarm when

the tripping temperature is reached, i.e. the output function " Th.O/L TRIP " is not ac-

The rated current of the device is taken as the base current for detecting an overload.

The setting factor k is set under address 4202 K-FACTOR . It is determined by the re-

lation between the permissible thermal continuous current and this rated current:

------------

The permissible continuous current is at the same time the current at which the e-func-

tion of the overtemperature has its asymptote. It is not necessary to determine the trip-

ping temperature since it results automatically from the final rise temperature at k · I

Manufacturers of electrical machines usually state the permissible continuous current.

If no data are available, k is set to 1.1 times the rated current of the protected object.

For cables, the permissible continuous current depends on the cross section, the in-

sulation material, the design and the way they are laid, and can be derived from the

relevant tables.

Please note that the overload capability of electrical equipment relates to its primary

current. This has to be considered if the primary current differs from the rated current

of the current transformers.

4206 CALC. METHOD

4201 Ther. OVER LOAD

4204 Θ ALARM

Th.O/L Θ Alarm

C53000-G1176-C156-2

Th.O/L Pickup

Th.O/L I Alarm