Archives

BASIC SECURITY

The basic security feature is present in the default offering of the 889 relay. The

889 introduces the notion of roles for different levels of authority. Roles are used as login

names with associated passwords stored on the device. The following roles are available

at present: Administrator, Operator, Factory and Observer, with a fixed permission

structure for each one. Note that the Factory role is not available for users, but strictly used

in the manufacturing process.

The 889 can still use the Setpoint access switch feature, but enabling the feature can be

done only by an Administrator. Setpoint access is controlled by a keyed switch to offer

some minimal notion of security.

CYBERSENTRY

The CyberSentry Embedded Security feature is a software option that provides advanced

security services. When the software option is purchased, the Basic Security is

automatically disabled.

CyberSentry provides security through the following features:

• An Authentication, Authorization, Accounting (AAA) Remote Authentication Dial-In

User Service (RADIUS) client that is centrally managed, enables user attribution, and

uses secure standards based strong cryptography for authentication and credential

protection.

• A Role-Based Access Control (RBAC) system that provides a permission model that

allows access to 889 device operations and configurations based on specific roles

and individual user accounts configured on the AAA server. At present the defined

roles are: Administrator, Operator and Observer.

Description of the 889 Generator Protection System

CPU

Relay functions are controlled by two processors: a Freescale MPC5125 32-bit

microprocessor that measures all analog signals and digital inputs and controls all output

relays, and a Freescale MPC8358 32-bit microprocessor that controls all the advanced

Ethernet communication protocols.

Analog Input and Waveform Capture

Magnetic transformers are used to scale-down the incoming analog signals from the

source instrument transformers. The analog signals are then passed through a 11.5 kHz

low pass analog anti-aliasing filter. All signals are then simultaneously captured by sample

and hold buffers to ensure there are no phase shifts. The signals are converted to digital

values by a 16-bit A/D converter before finally being passed on to the CPU for analysis.

The ‘raw’ samples are scaled in software, then placed into the waveform capture buffer,

thus emulating a digital fault recorder. The waveforms can be retrieved from the relay via

the EnerVista 8 Series Setup software for display and diagnostics.

Frequency

Frequency measurement is accomplished by measuring the time between zero crossings

of the composite signal of three-phase bus voltages, line voltage or three-phase currents.

The signals are passed through a low pass filter to prevent false zero crossings. Frequency

tracking utilizes the measured frequency to set the sampling rate for current and voltage

which results in better accuracy for the Discrete Fourier Transform (DFT) algorithm for offnominal

frequencies.

Overview

The relay features generator unbalance, generator differential, over excitation, loss of

excitation, 3rd harmonic neutral undervoltage, over and under frequency, synchrocheck

and other essential functions with a basic order option. Additionally available with an

advanced order option are overall differential (to protect the transformer-generator

combined), directional overcurrent elements, restricted ground fault, 100% stator ground,

out-of-step protection, rate of change of frequency, power factor, harmonic detection,

frequency out-of-band accumulation and others. An optional RTD module allows for

thermal protection and monitoring. An optional analog inputs/outputs module allows for

monitoring of generator excitation current, vibration and other parameters.

These relays contain many innovative features. To meet diverse utility standards and

industry requirements, these features have the flexibility to be programmed to meet

specific user needs. This flexibility will naturally make a piece of equipment difficult to

learn. To aid new users in getting basic protection operating quickly, setpoints are set to

typical default values and advanced features are disabled. These settings can be

reprogrammed at any time.

Programming can be accomplished with the front panel keys and display. Due to the

numerous settings, this manual method can be somewhat laborious. To simplify

programming and provide a more intuitive interface, setpoints can be entered with a PC

running the EnerVista 8 Setup software provided with the relay. Even with minimal

computer knowledge, this menu-driven software provides easy access to all front panel

functions. Actual values and setpoints can be displayed, altered, stored, and printed. If

settings are stored in a setpoint file, they can be downloaded at any time to the front panel

program port of the relay via a computer cable connected to the USB port of any personal

computer.

Introduction

The GE Multilin 515 Blocking and Test Module has the following features:

• 14 Pole switchbank

• CT inputs short when current switches are opened

• Current injection for each phase

• Ground terminal

• Ability to visually isolate (open) trip relay output circuits

• Cover provided

• Suitable for utility and industrial use

• 515 test plugs available

Description

The 515 Blocking and Test Module provides an effective means of trip blocking, relay isolation and testing of GE Multilin relays. By opening the switches and inserting test plugs, phase and residual currents from the primary CTs can be monitored. Currents can be injected into the relay from a secondary injection test set during commissioning.

Prior to testing, the trip and auxiliary circuits must first be opened to prevent nuisance tripping; CTs can then be shorted. Conversely, when the test is complete and the relay put back into operation, the CT switches should be closed first to ensure normal operation of the relay, prior to closing the trip and auxiliary circuits.

Installation

Shorting switches are provided for connection of 3 phase CTs (current transformers) and a separate core balance ground fault CT or 3 phase CTs connected for residual ground fault sensing.

When each CT switch is opened, the CT is shorted. It is essential that the CT is connected to the shorted side of the switch as shown in the following figure, otherwise dangerously high voltages would be present from the open circuited CTs.

When the switches are open, test plugs can be inserted to either inject signals into the relay wired to the switches or monitor signals such as CT current from the switchgear.

The 515 Blocking and Test Module consists of a metal chassis attached to the 515 test switches that slides into the panel. A single cutout in the panel, as per the dimensions shown in Figure 3, is required to mount the 515 test switches.