9
PN: 81127
Rev 4, 6/2017
5.
USB Interface
– the USB port is used to update the firmware in the SPI as well as update the
software in the STVI using a USB memory stick. It may also be used to download test results
from the STVI for download into another PC with Power DB software for storage or printing. For
control of the SPI, an Ethernet cable is provided. The STVI gets its power over the Ethernet
cable. Even though the STVI has a built-in virtual keyboard, the user can use a USB keyboard
with the STVI, as well as a mouse (including Logitech wireless mouse). The keyboard and/or
mouse are not provided with the accessories.
1.2
Terminology
The acronyms, terms, and definitions used throughout this manual are described below:
1.2.1
Glossary of Terms for Circuit Breaker Testing
The STVI display screens prompt the user to select, or set, various values. The values vary depending
on the protective device under test. Many of the terms used are similar in nature and mean virtually the
same thing regardless of the type of breaker. For example, the term Time Dial is commonly used to
define the time dial setting on the device under test. Unfortunately, some of the terms described here
may apply to different types of devices under test in different ways, and thus may not cover every
possible device made. However, it is hoped that this glossary will help the user to understand every
setting value on every device under test.
1.2.2.1
Pickup
(Tap / Sensitivity Rating)
A numerical value associated with a tap or sensitivity rating setting on the device under test. It is used to
define a setting value, pick up value, or minimum operating point, of the device under test.
1.2.2.2
Time Delay
It is a numerical value of time, normally associated with the minimum operating time of the device under
test. Low Voltage Power Circuit Breakers are available with three types of tripping characteristics: Long-
Time, Short-Time, and Instantaneous.
1.2.2.2.1
Long-Time Delay
The long time delay characteristic is normally associated with direct acting low voltage power circuit
breakers providing overload protection with typical time delays of approximately 10 - 60 seconds at 300%
of pickup.
1.2.2.2.2
Short-Time Delay
The short time delay characteristic is normally associated with direct acting low voltage power circuit
breakers providing protection for short circuit or fault conditions. It is used whenever a small delay is
necessary for coordination or selectivity with other protective devices. Typical delays of this type
characteristic are approximately 6-30 cycles.
1.2.2.3
Instantaneous
A numerical value associated with a tap setting of the instantaneous element of the device under test. It
is used to define a pick up value, or minimum operating point, of the instantaneous element of the device
under test. The instantaneous trip characteristic is used for short circuit or fault protection and has no
intentional time delay.
