Remote Devices - GE L90 Instruction Manual

5.7 INPUTS/OUTPUTS
a) REMOTE INPUTS/OUTPUTS OVERVIEW
Remote inputs and outputs, which are a means of exchanging information regarding the state of digital points between
remote devices, are provided in accordance with the IEC 61850 "Generic Object Oriented Substation Event (GSSE)" spec-
ifications.
The IEC 61850 specification requires that communications between devices be implemented on Ethernet
communications facilities. For UR-series relays, Ethernet communications is provided only on the type 9G
NOTE and 9H versions of the CPU module.
The sharing of digital point state information between GSSE equipped relays is essentially an extension to FlexLogic™ to
allow distributed FlexLogic™ by making operands available to/from devices on a common communications network. In
addition to digital point states, GSSE messages identify the originator of the message and provide other information
required by the communication specification. All devices listen to network messages and capture data from only those mes-
sages that have originated in selected devices.
GSSE messages are designed to be short, high priority and with a high level of reliability. The GSSE message structure
contains space for 128 bit pairs representing digital point state information. The IEC 61850 specification provides 32 "DNA"
bit pairs, which are status bits representing pre-defined events. All remaining bit pairs are "UserSt" bit pairs, which are sta-
tus bits representing user-definable events. The L90 implementation provides 32 of the 96 available UserSt bit pairs.
The IEC 61850 specification includes features that are used to cope with the loss of communication between transmitting
and receiving devices. Each transmitting device will send a GSSE message upon a successful power-up, when the state of
any included point changes, or after a specified interval (the 'default update' time) if a change-of-state has not occurred.
The transmitting device also sends a 'hold time' which is set to three times the programmed default time, which is required
by the receiving device.
5
Receiving devices are constantly monitoring the communications network for messages they require, as recognized by the
identification of the originating device carried in the message. Messages received from remote devices include the mes-
sage 'hold' time for the device. The receiving relay sets a timer assigned to the originating device to the 'hold' time interval,
and if it has not received another message from this device at time-out, the remote device is declared to be non-communi-
cating, so it will use the programmed default state for all points from that specific remote device. This mechanism allows a
receiving device to fail to detect a single transmission from a remote device which is sending messages at the slowest pos-
sible rate, as set by its 'default update' timer, without reverting to use of the programmed default states. If a message is
received from a remote device before the 'hold' time expires, all points for that device are updated to the states contained in
the message and the hold timer is restarted. The status of a remote device, where "Offline" indicates non-communicating,
can be displayed.
The GSSE facility provides for 32 remote inputs and 64 remote outputs.
The L90 provides an additional method of sharing digital point state information among different relays: direct messages.
Direct messages are only used between UR-series relays inter-connected via dedicated type 7X communications modules,
usually between substations. The digital state data conveyed by direct messages are 'Direct Inputs' and 'Direct Outputs'.
b) DIRECT MESSAGES
Direct messages are only used between UR-series relays containing the 7X UR communications module (for example, the
L90). These messages are transmitted every one-half of the power frequency cycle (10 ms for 50 Hz and 8.33 ms for
60 Hz) This facility is of particular value for pilot schemes and transfer tripping. Direct messaging is available on both single
channel and dual channel communications modules. The inputs and outputs on communications channel No. 1 are num-
bered 1-1 through 1-8, and the inputs and outputs on communications channel No. 2 are numbered 2-1 through 2-8.
Settings associated with Direct Messages are automatically presented in accordance with the number of
channels provided in the communications module in a specific relay.
NOTE
c) LOCAL DEVICES: DEVICE ID FOR TRANSMITTING GSSE MESSAGES
In a L90 relay, the device ID that identifies the originator of the message is programmed in the
!" !"
INSTALLATION
5-200
setting.
RELAY NAME
L90 Line Differential Relay
5 SETTINGS

5.7.6 REMOTE DEVICES

!
SETTINGS PRODUCT SETUP
GE Multilin