1 Introduction
Woodward oers a special G99-type-tested variant of the MRU4. It has some protection
settings xed or restricted to the value ranges that are specied and required in the
Engineering Recommendation G99 (Issue 1 Amendment 6).
If you need this MRU4 variant make sure to use the order code MRU4‑2xxxxx+G (with a
trailing “+G”) when you place your order.
(Note, however, that this “+G” is not shown as part of the typecode of the MRU4.)
This document details all the dierences between this G99-type-tested variant and an
ordinary MRU4, but without repeating the all the features that both have in common.
Therefore it is a supplement to the ordinary Technical Documentation of the MRU4, not a
replacement.
Background
The Engineering Recommendation G99 distinguishes the following types of power
engineering modules that have been installed after April 27th, 2019:
• Type A — connection point below 110 kV, 0.8 kW … 1 MW
• Type B — connection point below 110 kV, 1 MW … 10 MW
• Type C — connection point below 110 kV, 10.8 MW … 50 MW
• Type D — connection point ≥ 110 kV and/or registered capacity > 50 MW
Depending on the type to be protected, the EREC G99‑1‑6 makes the following
requirements for the voltage and frequency protection settings:
• The frequency and Loss of Mains (LoM) protection settings are xed in the rmware
of the protection device and cannot be changed. The settings that must be
predened by the manufacturer are explicitly given in Table 10.1 of the
EREC G99‑1‑6.
•The voltage protection settings are predened in the rmware of the protection
device. These default values are dependent on the type (dened above) and given in
Table 10.1 of the EREC G99‑1‑6. These settings, however, may be modied by
appropriately qualied personnel.
• Moreover, all settings that are permitted to be modied must be password-
protected. This way it can be ensured that only qualied users are able to alter these
settings.
Password-protected settings are a standard feature of all {?PLATFORM} devices, i. e.
not restricted to the G99-type-tested variant.
For the password-protection in general, see the “Security” chapter in the generic
MRU4 User Manual.
4 MRU4 MRU4-3.6-EN-G99
1 Introduction
