2.3.1 Demand Register. A demand register is the register on a demand meter
that indicates maximum load demand during a given interval of time, usually a
15- to 30-minute period.
2.4 Power Survey Recorder. To assist with electrical power surveys, a power
survey recorder (PSR) is recommended. The PSR is a microprocessor-based
instrument that accepts all necessary parameters for analysis of any
single-phase, two-phase, or three-phase electrical system. A PSR should
enable recording of electrical data for various loads to provide information
required for analysis. To allow demand analysis, the meter should be capable
of measuring kilowatt (kW) demand and make it possible for survey personnel to
correlate data acquired with time of day, day of week, or other time
designation. Other parameters often required for analysis are kilovoltamperes
(kVA), kilovoltamperes-reactive (kVAR), and power factor (pf). Knowledge of
any two of these parameters allows calculation of the third. The choice of
meter that allows selection of the parameter to be recorded will often save
time during analysis. When choosing a PSR, the following additional
recommended features are to be considered.
2.4.1 Portability. To enable different points in a system to be measured,
the PSR must be portable rather than fixed. Physical size and weight of
portable meters varies and may require consideration.
2.4.2 Full-Scale Ranges. Because of the range of load demands encountered
during a survey, a PSR should be able to measure both very small and very
large loads. PSRs typically have measurement limits of approximately 600 volts
and 1,000 amperes. Potential transformers extend voltage range and current
transformers increase current capability.
2.4.3 Split Core Transformers. Although it is preferable to install metering
devices before a load has been energized , many loads may be considered too
critical for shutdown. In such instances , split core transformers may enable
measurements to be made. With such devices, the circuit need not be
interrupted for insertion of current meter elements.
2.4.4 Accuracy. A PSR must be accurate across the entire range of scales and
parameters available. Poor accuracy reduces validity of calculations that are
based upon PSR data.
2.4.5 Temperature and Humidity Limits. A PSR must be capable of providing
accurate, reliable information in all climatic conditions encountered.
2.4.6 PSR Voltage and Frequency Requirements. Selectable voltage inputs for
a PSR is advantageous. Metering in various locations may give rise to
differing voltage requirements. Should voltage requirements exceed 600 volts,
PT will normally provide the needed additional capability. Although only one
frequency may be encountered at any particular facility, the PSR selected
should be able to measure power at whatever frequency is present.