Calibration of Synchronized Measurement System: from the Instrument Transformer to the PMU

Abstract

Even if their deployment in electrical medium voltage networks was not as extensive as could be expected at the beginning, Phasor Measurement Units are key elements for Smart Grid operation. An impressive amount of papers discusses their implementation and usefulness in medium voltage network and almost as many deals with their metrological characterization. Although it is well known that instrument transformers are the main source of uncertainty in PMU-based synchronized measurements, this topic is not sufficiently tackled in the scientific literature. In this paper, the attention is focused on the calibration of a measurement system made by a PMU and a low-power instrument transformer commonly employed in the Italian distribution network.

Compensation of Systematic Measurement Errors in a PMU-Based Monitoring System for Electric Distribution Grids

“…As for the random errors, vector ij is the vector of the six equivalent random errors associated with the six equivalent measurements in (10). ij is obtained from the voltage and current random errors by a matrix multiplication, using the same submatrices H ξ,α ij and H η,ψ ij as before.…”

“…, it is necessary to estimate the state x ij . The main idea is to use multiple measurement sets corresponding to different timestamps (giving us different equations (10), one for each time-tag t). In the next sections additional constraints are discussed and the estimation algorithm is presented in detail.…”

“…The development of PMUs specifically conceived for this type of network encourages the use of PMUs in many distribution applications [7], such as state estimation techniques applied to DNs [8], [9]. There are research projects aiming to design low-cost PMUs [10], [11] and at a large-scale installation in DNs [12].…”

Calibration Procedure to Test the Effects of Multiple Influence Quantities on Low-Power Voltage Transformers

“…Instead, the LPITs' calibration scenario is quite limited, but increasing day-by-day. For example, calibration techniques for electronic transformers are presented in studies by Tong et al [14] and Cayci and Kefeli [15], while in some studies [16][17][18][19][20] both current and voltage LPITs are tested at rated and off-nominal conditions. Finally, particular attention is given to the calibration of Rogowski coils and low-power current transformers (LPCTs) in other studies [21][22][23][24].…”

Error Model in Single-Board Computer-Based Phasor Measurement Units

“…The solution to the synchronization problem consists in this case in the direct triggering of the DAQ acquisition by using the PPS from the GPS module. The authors also discuss the calibration of such device over the entire signal chain, from the instruments transformer to the PMU [16]. A recent evolution of the same device relies [17] on a dedicated conversion stage rather than on a third party DAQ, on an innovative software PLL based on a Kernel module and on the use of the internal pulse width modulation block (PWM) to generate the sampling base.…”