IG-267-EN versión 01; 07/04/2017
15
General Instructions
ekor.rpa
Applications
The protection functions, available in models
ekor.rpa-110, which must be implemented to protect
distribution transformers with power ratings between 160
kVA and 2 MVA are the following:
• 50 ≡ Instantaneous overcurrent relay. Protects against
short-circuits between phases in the primary circuit, or
high value short-circuit currents between phases on the
secondary side. This function is performed by the fuses
when the protection cubicle does not include a circuit-
breaker.
• 51 ≡ Inverse time overcurrent relay. Protects
against excessive overloads, which can deteriorate the
transformer, or against short-circuits in several turns of
the primary winding.
• 51_2 ≡ Inverse time overcurrent relay II. Additional
step to protect against excessive overloads, which can
deteriorate the transformer, or against short-circuits in
several turns of the primary winding.
• 50N ≡ Instantaneous earth overcurrent relay. Protects
against phase to earth short-circuits or secondary
winding short-circuits, from the interconnections and
windings in the primary.
• 51N ≡ Inverse time earth overcurrent relay. Protects
against highly resistive faults from the primary circuit to
earth or to the secondary circuit.
• 51_2_N ≡ Inverse time earth overcurrent relay II.
Additional step to protect against highly resistive faults
from the primary circuit to earth or to the secondary.
• 50NS ≡ Instantaneous sensitive earth overcurrent
relay. Protects against phase to earth short-circuits of
very low value.
• 51NS ≡ Inverse time sensitive earth overcurrent
relay. Protects against highly resistive faults between
phase and earth of very low value.
• 51_2_NS ≡ Inverse time sensitive earth overcurrent
relay II. Additional step to protect against highly resistive
faults between phase and earth of very low value. 2
nd
Harm. Block ≡ Second harmonic blocking. Blocks
overcurrent units during transformer magnetisation.
In addition, the ekor.rpa-100 equipment, ekor.rpa-120
models, also have the following functions:
• 67/67N and 67NS ≡ Directional overcurrent relay,
directional earth fault relay and directional sensitive
earth fault relay. Phase, neutral and sensitive neutral
directional functions which are associated to their
corresponding overcurrent units, together allowing
directional overcurrent units.
• 49 ≡ Machine or transformer thermal relay. Protects
against thermal overloads of transformers which cannot
be detected by the overcurrent units.
• 46BC ≡ Broken conductor detection. Detects open
lines. Broken conductors are quite difficult to detect
using overcurrent units.
• 59/59N ≡ Overvoltage relay and residual overvoltage
relay. Protects against phase and neutral overvoltages
in the lines with 2 units for each phase and neutral, one
timed and the other instantaneous.
• 27 ≡ Undervoltage relay. Protects against phase
undervoltages in the lines with 2 units for each phase,
one timed and the other instantaneous.
The protection units that include the above mentioned
functions are:
Unit Type of cubicle
ekor.rpa-100 type = p
Fuse-combination switch
ekor.rpa-100 type = v
Circuit-breaker
Table 2.4. ekor.rpa-100-p/ekor.rpa-100-v
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