HPP Spilje is a part of HES Crn Drim. Ii is the largest accumulative hydro power plant in the river basin of the river Crn Drim located nearby Debar. With the commissioning in 1969 this hydro power plant is relevant source for electric power in the Macedonian electric power system.

HPP Spilje has accumulation with volume of 506.000.000 m³ water, out of which useful volume is 218.000.000 m³ water. The hydro power plant is located on the junction itself of the rivers Crn Drim and Radika, therefore the regime of the inflows in the accumulation depends of the regime of both the rivers. The inflows from the Crn Drim River during the year are quite equable due to existence of two accumulations upstream, the Ohrid Lake and Globocica accumulation. The inflows from the Radika River are quite variable which is due to the natural factors of the river basin..

History
1953 – 1962
During this period the Preliminary Design with Investment program are prepared

1963
The construction of the Main Design starts

1964
The preparatory works for the beginning of the construction start

1969
In June the accumulation filling starts and the same year in October HPP Spilje is commissioned

1990-2000
During this period the processes continue with better and more economical exploitation of the total hydro energy system. Also the process of redevelopment of the facilities begins in order to provide increased electricity production and increased generator output. In May, 1998 the Electric Power Company of Macedonia has signed loan agreement with the International bank for reconstruction and development (IBRD) – World Bank. The facilities of this loan are in amount of 61.5 million DEM were awarded to PC ESM for realization of the project “Project for improvement of the Electric Power System in Macedonia”.

2001-2005
With success was realized the project for rehabilitation of 6 hydro power plants in Republic of Macedonia, which is exceedingly important and complex project.
In general, the main 4 achievements of the rehabilitation of the existing hydro power plants in Republic of Macedonia are:

• Increased installed capacity in hydro-generation and improved primary and secondary.
• Increased hydro energy production.
• Decreasing the maintenance costs of the HPPs operation.
• Decreasing the possibilities for unscheduled outages of the hydro aggregates, HPPs and in general in the electric power system.

2014
With the completion of one of the most complex projects  – realization of the second phase of the rehabilitation of hydropower plants, installation of the new equipment for monitoring of the dams “Mavrovo”, “Globochica”, “Spilje”, “Tikves”, “Kozjak “and” Sveta Petka” was finished.

Within the project additional equipment was installed, for the automation of electricity production process and for auscultation and observing the conditions, stability and safety of dams and associated facilities.

Intake system
The intake tunnel under pressure, with length of 321,65m is installed on the right bank. The sill of the intake facility is situated on 546,00 maSL. The intake facility is equipped with drain and cleaning mechanism. The intake tunnel with 4.5 meters diameter is branched in three parts and the diameter of every branch is 2,20 m.

Dam and accumulation
HPP Spilje has stone deposit dam with height of 101 meters, which forms accumulation with total volume of 506.000.000 m³ water out of which the useful volume amounts to 217.000.000 m³ water. The normal projected accumulation level is 580 maSL and the minimal level is 560 maSL.

Hydro power plant
The hydro power plant Spilje is with installed capacity of 84 MW and annual generation of 272 GWh. The power station is 70m from the downstream dam scissor. In the power station there are 3 units equipped with Francis turbines with vertical axis, located on 485,75 maSL, as well as three phase synchronous generators. The power transformers are located outside the power station. The area between the dam and the powerhouse is used for locating of the plant 110kV.