1 Reasons for cost variance
In the process of analyzing the cost difference of power grid infrastructure projects, we should not only start with the external reasons of the projects, but also clarify the internal reasons behind the differences in engineering quantities and materials. In addition to the difference in the amount directly reflected in the budget estimates and final accounts, the reasons for the difference in quantity and price in the project are mainly concentrated in the following aspects: ① In terms of historical factors, the cost of power grid infrastructure projects will be greatly affected by relevant national policies and regulations. From the initial audit of the project, to the actual construction process and scheme of the project, and then to the final settlement audit, it is inevitably restricted and influenced by national policies and regulations. In addition to the progress of the project itself, the fund plan related to the project will also be affected by the changes in social and economic environment caused by changes in policies and regulations.
② In terms of environmental factors, environmental factors mainly include natural conditions, traffic, communication and surrounding residents. Site conditions will have an important impact on the project cost. For example, the overall layout of the project, "four links and one leveling" is directly related to the construction site conditions. (3) In terms of management factors, there will be many unexpected changes in the long-term construction process, so it is necessary to carry out project construction management according to the actual situation. A perfect, scientific and reasonable management system can effectively improve the level of project cost control and reasonably reduce the project cost under the important premise of ensuring the project quality.
1) During the construction of construction projects, due to inadequate management, there are often problems of engineering changes and over-budget. For example, many projects that need to be changed but have not been adjusted in the end, managers blindly sign visas, and the decision-making is not rigorous enough, and unnecessary sub-projects are arbitrarily changed, which affects the operational efficiency of construction projects. If we neglect management, pay no attention to the real-time construction situation and lack dynamic monitoring of the construction situation, we will not be able to feedback the construction situation in time, and we will not be able to track the use of funds to adjust the project cost, which will lead to the occurrence of over-budget. In addition, the lack of effective project cost control system will make the project cost control work lack of strong supervision, and it is difficult to effectively grasp and control the procurement of building materials, machinery and equipment and the construction cost management control during the construction process, which will most likely lead to the inability to fully carry out the project cost control work. Due to the lack of a perfect project cost control system, it is not uncommon that the rights and responsibilities of construction site managers are unclear.
Due to the imperfection of its own control system, once there are defects or other problems in the project, it is impossible to identify the responsible person in time and put forward the corresponding solutions in time, which will undoubtedly delay the construction progress of the project, lead to unexpected expenses and thus increase the cost. More importantly, it can not form a good guarantee for the overall quality of the project. In order to prevent the construction investment from exceeding the budget or wasting money, it is necessary to strengthen the management of the project from all aspects and details in order to better control the project cost.
2) On-site visa is a common management problem in construction projects. Modern construction projects have the characteristics of large investment scale, market-oriented price, high technology content, complex construction process and many units involved, so it is impossible to accurately predict the possible situation during the whole construction period and to stipulate all aspects in the contract. In fact, building materials and construction equipment are the key factors affecting the project cost. Whether their prices are reasonable and their utilization rates are appropriate is related to the overall cost of the project. [1] In addition, in the process of construction, the uncertainty in construction will increase with the changes of various subjective and objective conditions. In this case, on-site visa is inevitable, especially in engineering projects with complicated construction procedures or poor construction conditions, and the expenditure of on-site visa will account for a large proportion of the project cost.
(4) In the preparation of final accounts for completion, the preparation of final accounts is not in conformity with the regulations or unreasonable, which may lead to the problem that the construction project cost exceeds the budget. The final accounts personnel should take the final accounts preparation as the guidance, actively carry out the construction project budget preparation, carry out scientific and reasonable budget and final accounts work, and further clarify the final accounts amount. If the final accounts are unscientific and the contents of the final accounts are inconsistent with the actual situation of the construction project, it shows that the contents based on by the final accounts personnel in the budget work of the construction project are wrong. In this case, it will inevitably affect the accuracy of final accounts and lead to the problem of over-budget. Therefore, the importance of standardizing the preparation of cost final accounts is self-evident. If the compilation of cost final accounts itself lacks standardization, it will inevitably lead to many problems such as over-budget of construction projects.
There is a certain complexity in the construction project cost budget work, and at the same time, the professional quality of the cost final accounts personnel is required to understand the relevant policies and regulations and have a strong basic knowledge level. It is worth mentioning that the comprehensive ability of construction project cost final accounts personnel will directly affect the level of project cost final accounts. In the process of project cost budget, final accounts personnel should improve their professional quality and give full play to their expertise. If the comprehensive ability is poor, it is impossible to formulate a feasible final settlement plan of the project cost in combination with the construction demand of the building project. Many times, there will be a lack of comprehensive consideration, and there will be problems of missing items, which will lead to unreasonable final settlement results and many troubles and contradictions.
If the audit of final accounts is superficial and not strictly controlled, it is impossible to truly and comprehensively predict and reflect the actual expenditure of the project. In addition, sometimes due to the lack of understanding of the project, investigation, analysis and risk assessment, the final accounts personnel failed to enter the construction site for inspection, and the one-sided understanding of the actual project led to a large deviation between the actual construction and the cost budget, thus causing the problem of exceeding the budget. ⑤ In terms of investigation depth, in the early stage of formal construction, the relevant factors such as engineering designers and drawings have great influence on the project cost. Designers are mainly influenced by the comprehensive quality of personnel. Secondly, drawing design plays an important role in the construction stage, which is related to the cost control of construction projects. [2] Inappropriate design changes in the early stage of the project become design changes in the construction stage, thus affecting the project cost.
There are many possible reasons for design changes. First of all, the pre-preparation of the project is insufficient or the pre-consideration of the project design is too one-sided. For example, the survey data of the construction site is an important basis for the construction unit to carry out the project design budget estimate. In the investigation stage, the designer's investigation data on the geology, environment and area of the construction site are different or incomplete from the actual situation, which will inevitably lead to differences between the original plan and the construction process, resulting in a lot of design changes. During this period, all normal work will be affected, and personnel, materials, equipment and projects will stop running. On the one hand, the adverse impact of secondary design will delay the construction period, on the other hand, it will also cause claims with suppliers and cause economic losses; Secondly, the designer's working ability or communication ability may lead to the deviation between the design drawings and the construction standards and specifications of the project, which does not meet the actual needs and causes design changes; In addition, one-sidedness in bidding is also one of the reasons.
When evaluating bids, one-sided attention is paid to the design stage of bidding scheme, only to the better quotation, without considering the subsequent technical design and construction drawing design stage. Therefore, after the project bidding, the lack of competition mechanism leads to the decrease of the enthusiasm of the design unit to control the cost, which eventually leads to the problem of high cost. In addition to the above reasons, we should also deeply discuss the influence of some practical environments, such as the inconsistency between geological exploration results and reality, the change of construction site conditions, and the more complicated geological structure of the construction site than expected, which leads to the emergence of design changes. [3]
2 Five-dimensional analysis model of the causes of cost differences
In the process of analyzing the reasons for the cost difference of power grid infrastructure projects, the core idea is to sum up the factors affecting the project cost from the aspects of addition outside the bidding scope, construction drawing difference, change visa increase, policy adjustment and so on. Starting with the main reasons for the differences, this paper analyzes them from multiple dimensions, finds controllable factors and uncontrollable factors in different dimensions, puts forward corresponding measures and suggestions focusing on controllable factors, strengthens control and puts forward uncontrollable factors. Based on the above work, this paper puts forward several five-dimensional analysis models of the causes of cost differences of power grid infrastructure projects, as shown in figure 1.
Among them, the reason analysis of management dimension focuses on the bidding stage, finds and analyzes the list of bidding agencies and the quality of price limit compilation by stages, finds and analyzes the process cost control of construction management units, supervision units and settlement audit units, and analyzes the reasons for the increase in expenses. The reason analysis of design dimension focuses on the reasons for the increase of engineering quantity, whether the cost is increased due to layout upgrading, whether there is a phenomenon that design changes should be done but not done, whether there is a change of preliminary design principles, and whether the depth of survey and design is insufficient. The reason analysis of policy dimension focuses on the correlation between the rise of project cost and macro factors such as price rise, policy adjustment and tax and fee change. The reason analysis of the list dimension focuses on whether there are differences between the increase of engineering quantity and the items listed in the list. , while the cause analysis of other dimensions focuses on the analysis of other individual factors related to the increase of engineering quantity that have not been collected above.
3 cost analysis system and process
Based on the whole process management and control of typical power grid infrastructure projects, this paper carries out cost analysis and control mechanism research. On the basis of centralized inventory analysis, cost integration and the reasons for the change of engineering quantity, the cost differences of different types of projects with cost differences are analyzed by layers, so as to promote the whole process and all-round optimal management of the project and build an analysis and control system suitable for different types of projects, as shown in Figure 2. Combined with the multi-dimensional cost analysis model, the whole process of a typical project from feasibility study to construction is sorted out, and the cost analysis system of infrastructure projects as shown in Figure 3 is established. Its core mainly includes four modules: comparative analysis of difference between project settlement price and bid price, comparative analysis of settlement price and approved budget estimate, comparative analysis of settlement price and construction drawing budget investment, and comprehensive difference analysis. Through the comparative analysis of the prices of each link, the deep-seated reasons for the cost difference are further clarified.
3. 1 Settlement price and bid price difference module. This module comprehensively combines the process of project quotation and settlement of the construction unit, taking the bid-winning price as one of the analysis references, analyzes the reasons for the difference between the bid-winning price and the actual settlement price of the construction unit in the process of project bidding, clarifies the verification of workload visa and material price, explains the reasons and rationality of the change of workload difference, and determines that the settlement price in the project is more reasonable than the adjustment of the bid-winning price.
3.2 Settlement Price and Batch Estimation Variance Module. This module compares and analyzes the final accounts of the project with the approved budget of the preliminary design of the design department, compares and analyzes the costs item by item, summarizes the differences in quantities and prices between the final accounts of the project and the approved budget, clarifies the reasons for design changes and the rationality of the change plan, finds out the reasons for the differences in quantities and prices, and whether the main reasons for the differences in costs are proposed or changed in the construction stage.
3.3 Settlement price and construction drawing budget difference module. This module focuses on the comparative analysis of construction drawing budget and completion settlement price. Construction drawing budget is the most valuable data before the actual bidding work of the project. Through the comparative analysis of the settlement price and the construction drawing budget, the substantive difference between the actual construction link and the construction budget link can be clarified, and the internal factors of the cost change can be determined by combining the causes of the difference. 3.4 Comprehensive Difference Analysis Module. Based on the comprehensive analysis of the above modules, this module comprehensively extracts the links with obvious differences, determines the specific links with obvious differences in the cost of infrastructure projects, and finds the core reasons and key factors of the cost differences, thus completing the summary and combing of the cost differences of the entire infrastructure projects.
4 conclusion
In order to strengthen the cost management of power grid construction projects, a five-dimensional analysis model of cost difference is proposed, and the cost analysis system of power grid infrastructure projects is established, which lays the foundation for the subsequent power grid enterprises to establish a complete and effective cost control system and has long-term significance for promoting the sustainable development of power industry, realizing rapid economic development and maximizing social benefits.
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